Peculiarities of beef gut

Nowadays, most of the professional stringmakers use beef gut instead of sheep gut. From an historical point of view, the early use of this material dates back to the half of the xviii century but so far we have no evidence of a musical use of it. The industrial production of “serosa” type strings is made possible by machines called “slitting machines” that cut the intestines transforming them into stripes.

Further explanations on the video below:

Essentially, the portion of intestine usually called “runner” which has a diameter of 40 to 50 millimetres and a length of 40 to 45 metres is to be cut in two or three longitudinal stripes starting from the fatless part, meanwhile the remains (around three quarters of all the material) constitute the waste and will serve other purposes.

Sheep gut can instead be kept unsplit or be cut in the middle. The result of the second process consists in two stripes called “beef serosa” which are indeed a kind of “sandwich” made of two membranes: the first one is called layer 1, it has a longitudinal configuration and, consequentially, it is more resistant, the second, and weaker, one is called layer 2 and its fibres are in a diagonal order.

Because of the different shape and consistency of the two layers, their separation becomes necessary and it can be carried out by human personnel or by a specialised Machine. The presence of layer 2 in layer 1 stripes is the main cause of string breakages and unfortunately it cannot be predicted by simply observing them.

Layer 1 serosa type stripes measures are subjected to international standards used on sutures and tennis strings such as 19,16,14,8 mm in width and their length is based on frames used for industrial production of chirurgical threads and tennis (6 to 12 metres)

Later, the stripes form a pack called “bundle”, (made of a hundred strands) which is then salted n order to be preserved and transported.

The use of beef serosa has also brought surprising results:

  • High productivity , quick working process, low manufacturing cost
  • Easy reproducibility of the different batch of strings
  • High resistance to traction

Those advantages allow us to provide our strings to a numerous clientele at a remarkably convenient price, maintaining anyway a certain quality standard, this is a rare peculiarity when talking about sheep gut products. Hypothetically speaking, if string factories ceased to produce beef gut strings, the prices would literally skyrocket because In the past, there were hundreds of these factories, anyway, today the professional ones are just a few.


What about sonority?

It is often claimed that sheep gut stripes have better acoustic performances than their beef gut counterparts, nevertheless there is no scientific evidence of that, meanwhile is ascertained now that unsplit gut is superior to both of them.

The truth is that a string’s acoustic performance depends exclusively on its material’s specific weight and on its elasticity. The specific weight of beef and sheep gut is the same, in fact they are both made of collagen; regarding elasticity, it is dependant only on the way the string is made (and it’s measure is the twisting degree). Another important factor are the chemical processes used in stringmaking, which are always kept secret.

In the end, it is possible to produce excellent beef gut strings as well as tremendous sheep gut strings and vice versa.

Our beef gut strings are produced with an ingenious mixture between modern methods to obtain reproducibility, stability and a rapid production process, and old ones to gain the best sonority and durability.

Sugar Strings for Ukulele

Sugar strings

The  Aquila Sugar Ukulele strings are made using a blend with a recently discovered  plastic material derived from sugar- cane.
With a transparent look, the sound of these strings is clearly brilliant, clean and prompt.
Unlike the Fluorocarbon strings, these strings have an excellent vibrato and a significant timbre variation when playing very close to the bridge and then up on the sound hole. In other words, they contain in their extremes the sweetness and sing ability of Nylon and the clearness and promptness typical of Fluorocarbon. Another important property is the characteristic sustain, which by scientific measurements is superior to any type of string currently available in the market. Another feature checked is the sound projection: our scientific tests have shown that it is superior to that of the Fluorocarbon strings.
Although the surface is extremely smooth, the grip on the fingers is remarkable. The material is very clear and transparent similar to a crystal-glass.

Notice: at first use the strings might have a squeaky sound when you rub them lengthwise with the right hand, especially if you have dry or rough skin: that noise disappears in time, but if you want to get rid of it quickly, you can use a simple hand cream to moisturize skin and strings.

Hope you’ll have fun playing with our strings!!


Song  and Playalong

Would you like to by this product?

Click here!

Discover our sounds for classical guitar

Our direction is discovering new sounds

Curious to hear yourself what is the difference between our classical guitar sets?

On this page you can listen to the same opera played by the same guitarist using all our sets.

Composer: Sylvius Leopold Weiss 1687-1750
Opera: Ouverture (excerpt)
Musician: Alberto Rassu
Guitar: F.lli Lodi

The recordings were made with Zoom h2n without editing or post production.

Sound characteristics

The sets below are ordered by decreasing brillance of sound


Bright sound similar to Fluorocarbon but at the same time highly performing in vibrato, with great timbrical variation responding to variations of the right hand, and surprising sustain



The brightest and sharpest sound ever, superior to Fluorocarbon, sharp and clear promptness on sound attack, good timbre modulation



bright sound similar to Fluorocarbon but at the same time highly performing in vibrato, great timbrical variation responding to variations of the right hand, surprising sustain



Medium brightness and at the same time rich sound, allowing fair expressiveness



Excellent performance qualities similar to gut strings, with a better brightness than nylon but not as much as fluorocarbon, excellent sound attack


AMBRA 2000

The highest level of nuances and expressiveness on vibrato, excellent bright attack but never excessive, round and rich basses



Fairly brilliant tone, superior than the average tone of nylon, prompt and expressive sound, excellent vibrato



Warm and mellow sound, round and rich tone, good expressiveness and sweetness of sound that make them an ideal choice to fill the concert hall


Whole unsplit lamb gut: only a myth from the past, or are they really different?


whole unsplit gut string

In the production cycle of the XVI, XVII, XVIII and XIX centuries, the animals whose intestines were commonly used in the string-making industry in Rome, Naples, Lyon, Munich, etc. were both goat (expecially in Neaples area) and sheep intestines. The latter category was then subdivided into lamb gut, sheep gut and finally mutton gut.

In the slaughterhouses they used to treat any animal, always for alimentary reasons only; it was then up to the string-maker to select the intestines (coming from different sources and sometimes from very far away) according to their gauges, following the rule, that we have come to know, that the guts of smaller gauge had to be used only for the thinnest strings, and vice versa.

It is particularly interesting the singular situation found in Rome and Naples, where, during Easter time, huge quantities of lambs and young goats were slaughtered, whose intestines were then destined for the production of the Lute chanterelles, which were then sold throughout all Europe.

The common situation that is found in many Italian documents of the XVIII and XIX century is that with three or four whole guts you should get the range of diameters typical of the Violin first string: therefore, the original guts must have been really quite thin.



A Roman document from the mid-17th century (Attanasio Kircher, “Musurgia Unniversalis”, Rome 1650) even reports the interesting information that the first string of a Lute was made using only a single whole lamb gut:

The use of whole guts was therefore the rule in those countries (such as Spain, Portugal and Italy) where there was availability of small animals that allowed the use of three, sometimes four of their coupled and twisted guts, to obtain the range of diameters suitable as the first string of a Violin.

In other countries (France, Austria, Germany, etc.) the situation was quite different: their lambs, either for the breed, the climate or the type of feeding, were larger than those of Italy and Spain, and were never slaughtered at an early age (even for the good quality of the wool) , as opposed to what happened in Italy. Because of the larger intestine section, it was impossible to obtain suitable diameters for the Violin first string: this is the main reason for the huge orders of Lute and Violin first strings addressed to Rome and Naples by the various European nations in the XVII, XVIII and XIX centuries. There are several documents from the XVIII and XIX centuries, especially from France, which analyze well the situation and conclude that, because of their type of sheep, it was impossible to imitate the quality of the Neapolitan first strings.

This type of problem gave origin to the ingenious solution of splitting the intestine lengthwise and halfway in order to obtain thinner strips so as to circumvent the obstacle, a technique that is still used today by virtually all string makers, whether they deal with beef's casings or sheep's casings.

From the documents that were found, it would seem that this technique was introduced in Germany only in the late XVIII century (the German inventor won a prize from the local municipality), while its use was actually known as early as the second half of the XVI century, at least: in the statutes of the string makers of Rome in 1587, 1591, 1642 and 1678 it was in fact forbidden to make strings from intestines 'split in the middle', under penalty of heavy fines or even whip and jail and the  espulsion from the roman stringmaker’s corporation:



In the statutes of Lisbon string makers of the late 17th century it was also stated that a string maker who was discovered mixing whole guts with guts cut into strips would be forced to pay a hefty fine:


It would therefore be a commercial fraud. An Italian document from the middle of 1846 states that the use of strips to make strings instead of using the whole gut, is to be considered a fraud and it also explains how to detect it:



But why in Italy and Portugal were they so strict against those who cut / used the gut in strips? Wasn't it an ingenious system to be able to use even the larger and more available casings?

Until a few months ago, it was commonly believed that a string made from whole gut should have the same acoustic properties as a string made from strips. Our recent rediscovery of the ancient system used in Italy to make whole gut strings has instead shown a completely different reality: strings made of whole unsplit guts have greater acoustic performance, they reach a stable tuning more easily, they are more resistant to traction and also much more stable to climate changes as compared to the same string made out with the same intestine cut in strips.

This series of findings would definitively explain why the strings produced in Italy (and to a lesser extent in Spain) enjoyed the reputation that has always been praised in European documents from the late sixteenth to the first half of the twentieth century and also explains why it was so carefully monitored that there were no fraudulent initiatives by local string makers.


But does whole gut really sound better?


As mentioned earlier, uncut whole gut strings not only have proven acoustically high performance in terms of volume and achievable sound nuances, but also have high tensile strength, fast and stable intonation and resistance to climate changes. If we lived in those past times, we would have certainly done everything to preserve such quality by persecuting any form of fraud.

We asked ourselves what could be the reason for this better sound, stability and mechanical resistance: if we make two identical strings from the same gut (but one of which is obtained from strips) we get very different results.

We have come to the conclusion that the possible 'secret' of this special quality is the result of the natural conformation of the intestine, which presents on the one hand a sort of robust and thin longitudinal 'lace' on which the thin and delicate 'tubing' of the intestine adheres. During the twisting phase, it spreads around the above-mentioned lace which, on the contrary, results in traction at its ends, almost as if to create a hypothetical covered rope whose core is the aforesaid 'lace'.

Here is a video showing this:



What is the FL product?

I installed some new very high-quality strings, the nut is perfectly polished and graphite has been correctly applied into the grooves, but the first string keeps breaking when I get near to the final tuning: why?

“I bought a small harp for medieval repertoire, but unfortunately the strings of the first octave break right after being installed, even if they are from a well-known famous brand: why does that happen?

Here is the fact: you might have followed the best way to install the strings, and you might have used the best strings on the market, but did you ever look into the Breaking Index (also called FL product) of your instrument?

The FL product
When a gut string is gradually stretched, it will eventually reach a specific frequency at which the string will break abruptly: such frequency is called “Breaking Frequency”.

Counter-intuitively, such frequency will remain the same even with different diameters of the string (the only variation will be in the tension of the string, expressed in Kg).

The reason is this: if the diameter is increased of a certain percentage, the tension will also increase of the same percentage (and viceversa).  As a matter of fact, applying Mersenne/Tyler string formula, when changing the diameter and the resulting tension, it will be noticed that the frequency will remain unchanged.

As a consequence, both the following statements start from false premises, and therefore will result not true:

The string snapped: I decided to install a thinner one because it has a lighter tension and therefore it won’t break

The string snapped: I decided to install a thicker one because it is stronger

We have taken several measurements on thin gut strings (.40 mm diameter) of different brands, and the results show that the average frequency value at which a gut string with a length of 1.0 meter breaks is 260 Hz (more or less 240-280 range).

The Breaking Frequency (F) is inversely proportional to the vibrating length (L), so if the length of the string doubles and goes from one meter to two meters, the frequency will be half, and vice-versa. In other words, the product between the  parameters F and L is a constant that, at the unit length of 1 meter, is defined as the Breaking Index, or FL product.

When a luthier designs an instrument, he starts, instead, from the frequency of the 1st string: so, dividing the Breaking Index by the frequency in Hertz of the first (and therefore highest pitched) string, we can calculate the vibrating length at which the string will inevitably break.

Let’s make a practical example on a Violin:
The frequency of the first string, that is e" (considering the baroque pitch of 415 Hz), is 621.7 Hz
Therefore, the vibrating length at which the e" string will instantly break is:
260 / 621.7 = .418 m = 41.8 cm (this is the Breaking Vibrating Length)

Breaking Vibrating Length versus Working Vibrating Length
As we have observed, we can obtain the vibrating length at which the string will instantly break simply dividing the Breaking Index by the frequency of the first string, regardless of the diameter that will be used.

In order to have a string that does not break, it is therefore necessary to introduce a certain prudential shortening of this limit length, but by how much should we shorten it? If the shortening is excessive, the acoustic performance is compromised: the sound performance of a string, at the same tension and frequency, will be improved if its diameter can be reduced as much as possible by acting on the vibrating length (vibrating string length and diameter are inversely proportional).

To find the right answer, let’s take a look at the following graph:



It can be noticed how the string, at the beginning,  stretches a lot (this is the irrecoverable loss of elasticity, also called “false elasticity”) before following the linear stress/strain trend given by the Mersenne/Tyler law.
At some point that linear trend changes ratio, and the line gets steeper. This has only one explanation: the string has lost its ability to stretch; the breaking point is getting nearer, and it’s only 2 or 3 half-tones away.

Speaking of which, Daniello Bartoli in 1692 wrote: “a string shall break when it can stretch no more”:



Praetorious (‘Syntagma Musicum’, 1619) provides us with both the length measurement unit of Brunswich and the various tunings of the instruments represented in his tables: after deducing the possible standard pitch by the Praetorius's organ pipes, in most cases it was found that the various FL products reached the upper limit of the line (a clear reminder of the common rule of that times to tune the first string to the highest allowed, such as John Playford), right before the final steep section; we are therefore at two / three half tones far from the theoretical breakage of the 1st string.

This corresponds to a Working Index ( FL product) of 220-230 Hz/m on plucked instruments (i..e. 2-3 half-tones less than breaking point); 210-220 Hz/m for bowed instruments (3-4 half-tones less than breaking point), excluding large sized bowed instruments, that work around 190-200 Hz/m (see the several works of Ephraim Segerman in FOMRHI bulletins).



This is also confirmed by our calculations that we have carried out in some historical lutes and 5 course baroque guitars kept in museums, provided that the vibrating length has not been altered and that they can be traced back to a sufficiently identifiable standard pitch (see A. J. Hellis:’The History of Musical Pitch’, London 1880, and Bruce Haynes: ‘A History of Performing Pitch: The Story of “A” , 2002).

This is the case of surviving theorboes/ archlutes (for example those of Grail, Buechenberg, Hartz etc ) built in Rome in the 17th century (estimated St. Peter standard pitch around 390 Hz), renaissance lutes made in Venice in late XVI century- beginning of the 17th century such as for example those of Venere, Sellas, Tieffenbruchker etc  (Venetian ‘mezzo punto’: 465-70 Hz or 'tuon del cornetto'); 5 course guitars made in France in the late 17th/first half of the 18th century -such as the Voboam ones- (Royal standard pitch around 390 Hz), and, finally, 11,13 course  d minor german lutes in the 18th century ( Kammerton pitch, around 420 Hz), where the calculated Working Index ranged form 225 up to 235 Hz/m.

Is there a single Breaking Index, or more than one?

Until today, the average Breaking Index (i.e. the breaking point) of a gut string has been considered to be of 260 Hz/m (statistical average measurement taken by me on several modern gut strings with a diameter of .40 mm) while in the 1970-90 it was considered of 240 Hz/m (see Ephraim Segerman).

We have only recently come to understand that it is not possible to consider a single value for all sizes of plucked and bowed instrument: there are at least three Breaking Indexes that should be used (this finally solve the puzzle with the calculated Praetorius working index of the instruments of his tables)


Here is the deal: it is commonly thought that gut strings - whether they are thick or thin - are all manufactured following the same chemical procedures, applying the same twisting ratio; using the same type of gut and are finally produced following the same production phases.
Actually, this is not the case: in professional string making technology, at least THREE different types of manufacturing are (or should be) followed, which involve the use of different chemical baths, different twisting ratios, different types of raw gut and, finally, different manufacturing steps.
If we were not proceeding in this way, we could not effectively solve the two main underlying problems of a musical string: the breaking load (breaking point) and the Inharmonicity (i.e. the acoustic dampness, which is related to the degree of elasticity of the string, a parameter linked to the twisting ratio; type of raw material and chemical phases employed): these two parameters are in opposition to each other: increasing one will decrease the other (and vice versa).

Therefore, the different string diameters - especially those used as trebles - need their specific technology.
For example, it is not possible to produce a string of a certain thickness with the same technology employed for Lute trebles: the obtained string would be extremely stiff and hard, therefore totally dull.

On the other hand, it is not possible to adopt the technology used for the thickest strings (high twist) when manufacturing Lute trebles: the trebles would break long before they reach the required note.


The three types of gut strings

(these considerations are related to our own production. We cannot knows which is the situation of other stringmakers)

-The first manufacturing type concerns the super solicited and thinnest strings only – basically Lute and Baroque guitar trebles – where the one and only goal is to reach the maximum tensile strength and the maximum resistance to surface abrasion due to finger's action. The 'official' Breaking Index of 260 Hz/m refers precisely to this type of strings. No one, here, take care of Inharmonicity (these strings are so thin that there is no problem)

-The second type includes strings that are still considerably under stress, but not at the extreme levels that are typical of Lute/Baroque guitar trebles.
Typical examples of this type are the Violin and Gamba family  1st (except Pardessus)
Here the goal of the stringmaker is still to look for a high tensile strength, but at the same time beginning to reduce a certain degree of the inharmonicity by modifying the chemical process used.

-The third type is represented by the first strings of bigger stringed instruments such as cello, bassetto, G and D Violone and double bass: with these types of instruments, it is no longer necessary to research for a maximum tensile strength, so the manufacturing techniques aim to reduce the inharmonicity of the string of a good percentage but still not the maximum.

There would actually be a fourth type: the thickest strings that are never used as trebles. In this case, everything is aimed at reducing the inharmonicity as much as possible, taking absolutely no care of the tensile strength.
This is the typical example of the plain gut 3rd string of the cello, the 2nd ,3rd and 4th of the G and D violone (and sometimes even the 5th and 6th) and the 2nd and 3rd of the double bass - sometimes even its 4th string.

As we have seen, today the commonly adopted value for the Breaking Index of gut is 260 Hz/m which in fact represents only of the first type of gut strings: the Lute trebles (in our company this concerns diameters from .36 mm up to .50 mm).
Always referring to our company, diameters between .50 and .90/1.00 mm instead are made according to the typical construction criteria of the second type. Experimental data of Breaking Indexes make us converge towards a value of 240 Hz/m.
The third type is represented in our company by strings of diameters larger than 1.10 mm and up to 2.50 mm. We have not calculated the Breaking Index yet, but by extrapolation we believe that it is further reduced to about 220 Hz/m.

To sum up:
First type of strings (.36-.50 mm diameter): Breaking Index equal to 260 Hz/m
Second type of strings (.50- 1.10 mm diameter): Breaking Index equal to 240 Hz/m
Third type of strings (1.10-1.40 mm diameter approx.): Breaking Index equal to 220 Hz/m


How to put into practice all the above on our instrument?

Simple, by applying the traffic-light rule (this rule is only for plucked instruments; in the case of bowed instrument the orange light turns red, the green light turns orange): green light (little or no breakage risk), yellow light (possible medium risk of breakages, depending on intrinsic quality of the string, environmental conditions such as humidity and temperature, etc), red light (maximum risk, breakage is inevitable).

This is how to proceed: the vibrating length of the instrument, expressed in meters, needs to be multiplied by the frequency of the first string and then:

Lutes, renaissance and baroque guitars (diameters between .36 and .50 mm)
-if the value is less than or equal to 220: Green light
-if the value is between 220-230 : Yellow light
-if the value exceeds 240 : Red light

Violin, Viola da braccio, Gamba family Treble, Tenor and Bass (diameters between .50 and 1.0 mm):
-if the value is less than or equal to 200: Green light
-if the value is between 210-220 : Yellow light
-if the value exceeds 220 : Red light


Cello, G and D Violone, Double Bass (string diameters thicker than 1.10 mm):
-if the value is less than or equal to 190: Green light
-if the value is between 200-210 : Orange light
-if the value exceeds 210 : Red light


Of course, when tuning the same instrument to different standard pitches, all calculations will need to be revised and recalculated.

In our example of the Violin, the vibrating string length that generates the breakage must be reduced by two- three semitones.

The result is as follows: 34.5-33 cms (range of possible vibrating working length at the pitch standard of 415 Hz)


Essential fields of use

Harps in general (also modern harps)

This calculation is particularly useful on harps that, because of their great variety, might not respect this rule: one should mostly concentrate on the first octave, carefully verifying the FL product of either all strings or also in steps. This information should be taken into consideration by luthiers first of all, since they need to plan the harp according to known notes and pitch. Historically speaking, most harps work with the highest octave in conditions of yellow light

Medieval/reinassance instruments

Since no original instruments survived to this day (we make use of iconographic sources only), and the standard pitch of that time is unknown, it’s always worth verifying the FL product before buying any instrument. This information should be taken into consideration by luthiers when they are planning the instrument knowing the note of the first string and the standard pitch to use, as required by the customer.



Other fundamental applications of the FL product

How can a string maker understand when to change from a gut string to a wound one?

How to understand when a gut string will not have acceptable acoustic performances anymore?

I installed all gut strings on my bass Gamba, but the 6th string doesn’t perform well

I’d like to install all gut strings on my Viola: can this be done?

I installed very good pure gut basses on my Lute, but they are still too dull: why?


The FL product is the answer. If on the first string the FL product is also called Working Index, on the other strings this index itself can express the Inharmonicity degree of that particular string in the instrument, having the vibrating string length and the frequency.

Generally speaking, the Inharmonicity degree can be considered as an index of acoustical quality; it will be maximum on the first string, and it will gradually decrease on lower strings until the FL product, and consequently the acoustical performance of the strings, will be reduced to a point where human ear will not perceive it as acceptable anymore (it is widely known that strings of growing diameters, placed on the same vibrating length, will become more and more dampened, will be difficult to be brought into vibration, and will give bad acoustic performances).

At that point the only solution is to adopt a different type of strings (wound, roped, KF, loaded, etc).

How can one predict when to adopt such different technological solution?

Looking at the FL product, of course!

An example for the classical guitar (and all plucked instruments, in general):

The 3rd string – the ‘g’ – of a classical guitar is the last nylon string; its FL product is around 127 Hz/m (using a scale of .65 m and a frequency of 196 Hz for the ‘g’ note, that it is to say A-440 pitch standard)

The 4th string – the ‘D’ – is instead a wound string; its FL product is around 95 Hz/m (on a scale of .65 m and a frequency for the ‘D’ is of 146.8 Hz)

The principle behind this transition is that a plain nylon or gut string will not be able to give good acoustical performances when its FL product will be lower than 90-100 Hz/m (on the 5th course of the Lute, the FL product is around 70-80 Hz/m only, but the work around is using two strings paired in octave).

Working with the 1st string at 225-235 Hz/mt, the 6th course of a Lute will have an FL product of 59-60 Hz/m; the inharmonicity issue is here resolved only using two strings paired with the octave (see Tinctoris 1474 and Virdung 1511) , but this is the lowest limit: under 60 Hz/m the acoustic performance becomes so poor that even a paired octave will not help. Therefore there’s the need to change to a type of strings that will work down til, to the lower limit of 39 Hz/m (wound strings, KF, loaded, Gimped, etc); i.e. a 'densified' string.



On bowed instruments, thanks to the continuous action of the bow on the string, the situation is better: in this case, the lower FL product before to switch to a densified string (wound or loaded) can be considered around 60-70 Hz/m .

With that being said, it is still possible to have a good performance also when the FL product for the 6th string is of 57-58 Hz/m only (scordatura), provided that the gut strings of the 5th and especially the 6th strings have a very high elasticity and/or density (roped structure/loaded gut/whole lamb gut). (1)

However, care must be taken so that the FL product should never be under 55-56 Hz.m: under this value, wound strings (or loaded strings) need to be used.

This is the situation that commonly happens with all those instruments whose FL product of the 1st string is lower than 200-210 Hz/m.

For example, the 6th D string of a Bass Viol with a scale of 69 cm (at 415 Hz pitch standard) has an FL product of only 48 Hz/m:  if such instrument would have been designed to use only gut strings, using the right FL product for the 1st string (i.e. 210-220 Hz/m), the FL product of the 6th would raise up to 57-58 Hz/m; as a consequence, the instrument would have a scale of 77 cm, and not only 69 cm. John Playford 164 etc wrote that the 1st string of Treble, Tenor, consort bass and Lyra viol must be tuned as high as possible.

The g string for a Violin at 415 Hz shows an FL product of 61 Hz/m: this means that a pure gut string can be still used, provided that it’s of excellent quality (i.e. very well twisted). On the other hand, it’s impossible to employ a plain gut strings for the  C string of the Viola da Braccio (even it is very high twisted) that has a vibrating length of only 38 cm: its FL product is of 47 Hz/m only.

To have a plain gut low c,  the vibrating length of the  Viola da braccio  should ensure an FL product like of the Violin G string: i.e. 61 Hz/m (in any case, not less of 57-58 cm). Therefore, following the fore mentioned proportions, its vibrating string length should be 47-48 cm (or at least 43 cm as absolute minimum value; as to say  the same FL product of the 6th string on the Gamba family).

Vivi felice

Mimmo Peruffo


(1) In the case of the Cello, the situation is different: during the 18th century, this instrument never used roped gut strings or loaded strings, in favour of high-twist gut strings instead. In general, cellos worked with higher tensions than those in use on the viola da gamba family: the combination of 'higher tension and high-twist gut strings' can negatively affect the sound output and the quality of the bow's attack. This suggests that when the FL product of the third string is below 70 Hz/m, it is better to use a wound string.

Wound strings for bowed and plucked instruments from the late 17th century to the early 19th century: what do we know?


Nowadays, the first known mention of the appearance of wound strings dates back to 1659 (Samuel Hartlib Papers Project; Ephemerides: “Goretsky hath an invention of lute strings covered with silver wyer, or strings which make a most admirable musick. Mr Boyle. […] String of guts done about with silver wyer makes a very sweet musick, being of Goretskys invention”), followed then by John Playford (“An Introduction to the Skill of Music…”) in 1664. But their further distribution, in the first decades after their appearance, was not at all fast, but non homogeneous and scattered, at ”Leopard spots”.

Italy, a country that has always been renowned for the production of harmonic strings, offers us a document from 1677 where, in an invoice by the luthier Alberto Platner, one can read: due corde di violone, una di argento et un’altra semplice
(“… two violone strings, one in silver and the other one simple…”).

The first iconographic representations of stringed musical instruments using such strings date back to after 1690 (see the pictorial artworks of Anton Gabbiani, Florence, or of the French painter Francois Puget, Paris 1688, and other authors).

According to Rousseau (Traité de la Viole, 1685), it was the violist Sainte Colombe who first introduced them in France around 1675, but the main English treatise for Lute and Bass by Viola dated back to the second half of the 17th century (Thomas Mace: “Musick’s Monument”  London 1676) still does not mention them, but only describes basses in pure gut: the Lyons and the dark red Pistoys.

Claude Perrault (Ceuvres de physique […], Amsterdam 1680 pp. 214-5) has one of his paragraphs titled: “Invention nouvelle pour augmenter le son des cordes” (“New inventions to augment the sound of a string”). This is certainly regarding wound strings.

In James Talbot’s manuscript (1700 circa) the basses of Lutes, Violin and Violin Bass are still the traditional ones, in only gut: that is, the Lyons and the Catlins.

In the first decades of the eighteenth century, wound strings took over almost everywhere compared to the traditional gut only basses, on both plucked and bowed instruments, totally revolutionizing the way of making music up to the present day.

A recently discovered Roman document, dated 1719, not only states in writing for the first time the use of a fourth wound string on the Violin, as an alternative to the usual naked gut, but also states its construction data, in other words the diameter of the core and the wire to be used (see Patrizio Barbieri, 2016: “Musical instruments, gut strings, musicians and Corelli’s Sonatas at the Chinese Imperial Court: The gifts of Clement XI, 1700-1720”).

An important testimony regarding the use of a fourth wound string comes from Count Giordano Riccati (“Delle corde ovvero fibre elastiche… ” 1767) and then, along the course of the 18th century, also from various other Italian, French, Austrian, German and English documents, where the use of wound strings is described also for the following instruments: Viola da braccio, Cello, Double bass, Viola bass and finally Pardessus.

From the middle of the eighteenth century, however, the use of wound strings became a standard everywhere; around 1750-60, the Cello switched to using a wound string also on the third one.




  1. Use of exclusively round wire;
  2. Use of metals such as copper, pure silver, silver-plated copper and brass. There were still no metals such as aluminum, tungsten (or wolfram) or special alloys which began to be used only in the first half of the 20th century.
  3. High-twist natural gut core;
  4. No silk between the core and the covering wire;
  5. Different balance between core and metal winding compared to modern coated ropes (even if made on a gut core).

The strings were made using very simple winding machines:

winding machines


winding machines




The types of wound strings used between the end of the 17th century and the end of the 18th century can be traced back to three varieties:

  • wound strings on a gut core with close metal winding;
  • wound strings on a gut core with open coil winding;
  • wound strings on a gut core with a double metallic close winding.

In the second half of the 18th century, type 1 strings began to be manufactured also on a silk core, but only for plucked instruments (practical tests carried out by us have shown that coated silk strings do not work well under the bow). The strings with close winding on a gut core were those that characterized the entire nineteenth century until the early decades of the twentieth century, when, right after the Great War, those spun in aluminum and/or with partially polished metal wire began to spread.

In the 18th century, type 2 strings were called ‘a demì‘ or more generically ‘demifileè‘ strings by the French.

Their construction characteristic is clearly deducible from their name: their winding had a spacing between the loops equal to the diameter of the wire, or slightly more for plucked instruments (this precious construction indication – the only one of the eighteenth century – comes from Le Coq, Paris 1724, regarding the strings for the five-course Guitar):


For bowed instruments, it is assumed that the metal wire was more spiralized (this way, the horsehair of the bow was not channeled):


This is our translation of what Stradivari wrote: ’Questi sono i campioni delle tre corde grosse; la corda che mostra attraverso le sue spire che l’anima è fatta di budello và ricoperta con una spira molto aperta ad imitazione della pianta Vitalba

(These are the samples of the three large strings; the string that shows through its coils that the core is made of gut should be covered with a very open spiral as an imitation of the Vitalba plant)

the Vitalba plant

An example of the Vitalba plant


The first mention of this type of string, however, dates back to 1712 (Sebastien De Brossard: ‘Fragments d’une méthode de violon’, manuscript), while the last of our knowledge is dated 1782 (Jean-Benjamin De Laborde ‘Essai sur la musique ancienne et moderne’).

The demifilèe strings – always made on a gut core – were used in France sometimes both as the fourth c-string of the seven-stringed viola bass (see the letter of G. B. Forqueray to Prince Friederich Wilhelm of 1768) and as the third of the violin (Brossard 1712 and Laborde 1782):


Five-course Guitars

In addition to the already mentioned Le Coq (1724), we have further documents that confirm the use of wound strings having both gut cores (Corrrette 1761 ca) and silk cores (Don Juan Guerrero: “Methode pour Aprendre a Jouer de la Guitarre”. Paris 1760):

4-course and 6-course Mandolins

Documentation from the 18th century testifies both to the use of demì strings on a gut core and bass strings with close winding on a silk core or even gut (Methods of Fouchetti and Corrette, Paris 1771-72):

Lutes and Gallichons

The first mention of the actual use of wound strings on gut cores dates back to 1715 (Germany); several other French and, above all, German written sources from the 18th century were later discovered, confirming the fact that the 11- and 13-courses lutes used wound on gut cores. Some clues, both in terms of surviving artefacts and iconography, lead us to believe that they were of the demifilè type (we made exhaustive tests using a silk core, but they led to rather disappointing results, both in terms of acoustic quality and mechanical nature).

For example, here are some fragments of bass strings found on a lute by Raphael Mest in Linkoping (Sweden) followed by a German/Austrian iconography presumably from the middle of the 18th century:


Example of a 13 course d minor lute equipped with demifilè basses wound on a gut core considering all the historical information


On the Gallichon, we found this interesting iconography of German origin dating back to the mid-eighteenth century that, together with general considerations on the construction characteristics of the instrument, strongly suggest the use of close wound basses on a silk core (as already used on the 6-courses Spanish guitar), a hypothesis supported by our practical tests:



Historical documentation and French iconography bear witness to the use of wound basses on silk cores (Baud, 1797-98, Versailles) as well as demifilè, presumably on gut cores:

(Note the strings of the violin behind the harp: 4th wound in silver, and three gut strings)

At the end of the eighteenth century the demì strings went into disuse both because of the disappearance of the specific instruments that used them (viola bass, 5-course guitar, lute, etc.) and because they were replaced, in the plucked instruments, by those of type 1, wound on a silk core, that led to the appearance of the simple 6-string guitar:

Example of wound bass strings on silk cores, for 6-course Spanish guitar, dated back to 1810-12



Contrary to common belief, the demifilèe strings were not strings designed to have a ‘transition’ sound between the upper nude gut strings and the following close wound basses. To achieve this, a normal close wound string with a core-to-metal wire ratio in favour of the core would have been sufficient. The real reason is of a technological nature: research into 18th century wire technology has brought to light the fact that at that time they were not able to make wires so thin as to be able to access the close winding (for example, the thinnest gauge on the Creyseul scale, mid-18th century, concerning the gauge of wire for harpsichord is No. 12, equal to about 0.15 mm). See also on this subject: James Grassineau: “A musical Dictionary” London 1740).

The solution of covering a core by spacing the metal wire brilliantly solved the problem, but introduced a new one linked to the potential difficulties of conducting the bow and to the fragility of the metal winding at the nut.

Type 3 strings:

It is supposed that they were also used during the eighteenth century (G.B. Forqueray in his letter of 1768 explains to Prince Wilhelm that the lower strings of the viola bass should never be made double-covered but with simple winding: this is a clear indication that the double-covered strings were still known/used in those days); this means that, perhaps, they were a strategic solution for those particular bowed instruments characterized by having a very short vibrating length in relation to their tuning.

To cite, for example, the Violoncello/Viola da Spalla but, to be more sure, also the 5th low-B string added to the Double Bass in the late 19th century.


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How to correctly install strings in order to avoid breakages and at the same time assuring a fast and stable intonation

At times here in Aquila we are told: “I installed the first string and it broke, so I tried with a second one and it ended up the same way. What can I do? …

Sometimes, though rarely, it happens!

Therefore, we have created a short guide that will allow you to achieve the maximum performance in short times, avoiding potential breakages and false notes during installation.

All you need is to follow these directions:

  1. After installing the string, tune it out of the slot of the nut. You will insert the string in its groove only when you’ve almost reached the desired final note: this technique ensures that the string has the same tension both in the peg-nut portion and in the nut-bridge portion, and at the same time it avoids potential unpleasant breakages, since we can never tell if the grooves of the nut, that are also points of friction, hide unexpected cutting points.
  2. To help the string stretch evenly without introducing false notes and become stable faster, pull it at the 12th fret during installation, repeating it until the tuning variation after each pull gets minimum.
  3. The strings need a few days after first installation to develop their full sound, so we suggest to install them and then wait at least an overnight before using them professionally.


The following videos summarize all the above mentioned recommendations:





How to correctly install gut strings in order to avoid breakages and at the same time assuring a fast and stable intonation

At times here in Aquila we are told: “I installed the first string and it broke, so I tried with a second one and it ended up the same way. I have been playing the [violin/viola/cello/gamba] in the last thirty years and I sure know how to install a string…


But being expert musicians and performers is enough to be considered expert installers of gut strings as well?


Critical characteristics of gut strings

As a matter of fact, due to its natural origin, at times a gut string can present a problem: in this case we talk about defective strings.

A string can be called defective when:

  1. it has been excessively polished: at touch and at sight the string may appear good and perfectly smooth, but in fact the external fibers have been excessively damaged, so, little after its installation, the broken fibers will raise from its surface as tiny hairs.
  2. it has very small whitish marks (fat spots) on the inside: such strings tend to break during the initial tuning
  3. it suddenly breaks once installed, far from its constraint points (bridge and nut)

A gut string in itself is very  strong to traction, but it also has some weak points:

  1. the material is not hard, so it suffers from potential sliding or contact points that are even minimally sharp (sharp edges)
  2. it easily absorbs humidity, so in humid environments the string becomes less compact, softer and therefore gets even more delicate on the sliding points
  3. it leads to high friction on contact points, at times it squeezes on the nut and bridge slots, or it may not slide smoothly.

Common solutions, like applying some graphite on the nut grooves, are pretty useless if the slots have not been appropriately created following the criterions suitable for gut strings, like in these examples:

The most important things to be observed, is that the slots are slightly cut and they never have clear bending points, and lastly that the nut is mirror-polished. Only at this point using graphite on the grooves becomes truly effective.

The historical essays, such as Thomas Mace’s Musik’s Monument (London 1676), suggest how the nut of a Lute should be prepared in order to avoid breakages and obtain tuning stability:

Finally, iconographic sources of the XVII century often show a particular nautical knot, called Bowline, that divides in half the traction of the string in two distinct points at the hole on the tailpiece (such use can be limited to the first and highest pitched string)

This is how to tie a Bowline knot:

There are also some other best practices to follow:

  1. tune the string keeping it out of the nut slot and, for bowed instruments, every now and then lifting the string from the bridge: this prevents the sliding on friction points, and assures an even tension on both sides of the constraint points. Put back the string in its slot only once tuned (or very near to its final tuning);
  2. Once in a while, it’s good practice to gently pull the string at half of its length, in order to unload its not recoverable elasticity and at the same time clamping it on its constraint points (this way the string will be almost immediately ready to be played);
  3. Put the string in tension slowly: the material needs time to reach its final state of stretching;
  4. The portion of the string wound on the peg should be as small as possible, making sure that on the first loop the string passes on top of itself, and then closing the spirals without further overlaps: see the indications of Thomas Mace on Musik’s Monument (London 1676).


The following videos summarize all the above mentioned recommendations:

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Mimmo Peruffo

South America and Spanish Instruments


The sound of these strings is clearly brilliant, clean and prompt, and provide great acoustic power. Unlike Fluorocarbon strings, these strings have an excellent vibrato and a remarkable timbre variation when played very close to the bridge and then up over the sound hole. Laboratory tests showed that Sugar strings have a projection of sound (measured in Joules) and a sustain respectively 24% and 18% more than fluorocarbon strings.

These strings have, in their extremes, the sweetness and singability of gut and the clearness and promptness typical of Fluorocarbon. Another important property is the characteristic sustain, which by scientific measurements is superior to any type of string currently available in the market.

Another measured feature is the sound projection: our scientific tests have shown that it is superior to Fluorocarbon strings. Although the surface is extremely smooth, the grip on the fingers is remarkable; in other words it is never slippery.

In the event of a squeaking sound that appears at the beginning under the right hand fingers, it is suggested to use a hand lotion, or even better a softening paste used to adhere to sheets of paper.

To learn more about sugar strings clik here:


This material gives a unique feeling and a strong, consistent sound. Until recently, it was necessary to increase a string’s gauge to get a lower-pitched note. But increasing the string’s diameter also increases internal dampening. That makes the string less bright, less responsive and more muffled; the thicker the string, the duller the sound. Our revolutionary new approach — unique to us — changes the specific weight of the material, increasing it progressively to leave the gauge almost unchanged.

The result is amazing: instruments sound brighter, more powerful and more responsive through the entire range of the fretboard. The strings also maintain their intonation better, because thicker strings need to be fretted harder, pulling them further out of tune.

To learn more about Red Series link here:


This material was discovered and perfected in our laboratory after a long period of research and after being thoroughly tested, thus giving rise to a new synthetic product of high technology.

Just like gut, the Nylgut® is liable to suffer from cutting edges. Before stringing the instrument do make sure the nut and bridge are free from sharp edges and the nut grooves not too deep and perfectly smooth. You can get rid of sharp edges with very fine grit sandpaper (600, for example) or the finest steelwool (000).

The best sound quality develops when the strings have completely set, which may ordinarily take sometime. To achieve a stable intonation in just a few minutes you can repeatedly pinch each string at midlength with your fingers, pull it decidedly sideways and tune it up again. Stop when the string does not pull out of tune anymore.

To learn more about Nylgut:

Equal tension/ equal feel: some useful information

Equal tension/ equal feel

In this last decade, the so-called equal tension setting has grown very popular among many players of historical bowed instruments, with the belief that such setting is the exact scientific interpretation of what was being done in the past (and what has been found on some historical documents, especially regarding the Lute): strings must all have the same ‘tactile sensation/equal feel’ of tension.

Physics can prove mathematically that strings that show the same deviation gradient, when an identical weight is applied at the same distance from the bridge, will also have the same tension expressed in Kg (the same deviation gradient produce also an equal feel of tension under the fingers).

What has not been considered, though, is the fact that this mathematical relationship is true only when strings are already in their final state of traction, while it proves to be false if the theorical diameters are calculated using the same value of tension in the Mersenne-Tyler string formula, like most of the equal tension supporters do nowadays.

Huggins, in the late XIX century, was already aware of this difference (just like the count Riccati in 1760).

This is what really happens: when undergoing the same weight, the thinner strings, in percentage, will experience a higher thinning as compared to the thicker ones.

In other words, once they are set into their final state of traction (i.e. intonation), each string will get thinner by a percentage that depends on the twisting ratio and how it was realized (high twist/low twist/roped etc) and expecially its Working Index into the instrument (the FL product).

Such percentage will be maximum for the high-pitched thinner strings (i.e. chantarelles), while it will be gradually lower on the thicker ones .

If the string formula is then applied to the new diameters measured once the strings reach the final tuning (and therefore they are in their final state of traction/tuning), it will be observed that tensions will follow an inverse scalar profile, and also the tactile sensation/feel of tension will necessarily feel reversed as well (minimum on thinner strings, maximum on the thicker ones).

We therefore physically performed all the tests as described by Di Colco, Mozart and Mersenne, contradicting the results that apparently seemed to confirm the “equal tension” hypothesis using the Mersenne/Tyler string formula.

Mersenne itself not only wrote that no player of his time followed his indications, but also introduced a 1/16 corrective coefficient to the string formula, without giving any explanation, and causing some criticism (for example see Daniello Bartoli, 1692).

Attanasio Kircher (“Preludium1”, 1650) provides the number of gut casings needed to make Roman Violon strings:

Est hic Romae Chelys maior, quàm Violone vulgo vocant pentachorda, cuius maior chorda consesta est ex 200 intestinis. Secunda ex 180. Tertia ex 100. Quarta ex 50. Quinta denique ex 30. (19)

These details are very interesting and unique because they define the number of guts to be used to make the strings for this large instrument.

To verify the tension profile from other historical information we know that with three  whole unsplit lamb guts we obtain an average diameter of 0.70 mm (See De Lalande and Count Riccati) . The following is obtained by simple proportion:

1: 2.21 mm (30 guts)

2: 2.85 mm (50 guts)

3: 4.04 mm (100 guts)

4: 5.42 mm (180 guts)

5: 5.71 mm (200 guts)


The Chelys Maior is tuned as follows: E, A, DD, GG, (and lastly FF)

Let’s calculate the tensions considering a ‘Roman’ pitch of 392 Hz and a vibrating length – assumed by us –  of 90 cm. This is the data obtained:

1:  E – 35.50 Kg

2:  A – 26.31 Kg

3:  D – 23.54 Kg

4:  G – 18.88 Kg

5:  F  – 16.64 Kg


The tension profile has a scalar pattern: this is a direct example from the 17th century that demonstrates the scalarity of the tension expressed in Kg. By practical test this tension profile is also very close to an equal feel.

Unfortunately, none of today’s supporters of the equal tension, to the best of our knowledge, has ever done verification tests on what was stated on such documents, therefore trusting blindly what has been written.

As a conclusion, to recreate an “equal feel” setting, the theoretical calculation by the string formula must consider a certain degree of scalar tension.

When calculating our strings, we consider the correct scalar gradient: that’s why we are able to offer “equal feel” settings as they were used in the past, and that’s also the reason why we decided not to prepare “equal tension” settings by the string formula that have no real historical support and create disadvantages to a good musical performances, as Huggings and count Riccati already underlined in the XVIII and late XIX century.

We suggest to inform all customers about this topic, in order to finally clarify this point and avoid the practical difficulties encountered recently when calculating existent string settings.

To know more on this topic:

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Mimmo Peruffo