In the area of written sources, a passage in the Mary Burwell lute tutor (c. 1670) could not go unnoticed. In chapter 16 dealing with two headed lute introduced by English Gaultier, the author complains about the problems caused by "...the confusion that the length of sound produce it alsoe..." and "...every basse sound make a confond with every string". The above mentioned two headed lute is the one depicted in the well known portrait of English Gaultier and in many other 17th century Flemish sources. Such an instrument may perhaps be identified with the lute made by Raphael Mëst in 162..., now in the Linhöping library in Sweden, whose extended string length is less than 90 cm (26), roughly in line with the measurements given by J. Talbot for this type of instrument. At such vibrating length such an overpowerful persistent sound, so to make the anonymous author complain and lutenist revert to use lute without extension, is in no way justifiable, for unloaded natural gut strings, no in after what twisting method is adopted, which anybody can easily verify.

Another source deserving attention is a report by Claude Perrault: (document 9) "...c'est par cette même raison que la maniere que l'on a inventée depuis peu de charger les cordes a boyau, rend leur son beaucop plus fort: car le fil de metail trait..." (27). The author refers to the new overspun bass strings giving however the impression he is talking about a new technological strategy for loading gut (i.e. the use of metal wire) in place of a more traditional one.

As far as 17th century lute treatises are concerned, such as Robert Dowland's (18) and Thomas Mace (10) for instance, the most interesting information (besides confirming more or less explicitly the strings smoothness) is the subdivision of strings in classes according to their specific use on the instrument. In Mace's treatise, for instance, three classes are defined: strings suited only for treble registers and the higher basses octaves (Minikins, Romans), strings for mid-range registers and the other basses octaves (Venice catlins) and finally strings exclusively used for basses (Lyons, red Pystois) (28). This "acoustic specialization" of strings induces to get over the idea of just one manufacturing system, in favour of a complex technological diversity, indispensable to grant a finished product possessing the acoustical and physical features necessary, from case to case to obtain maximum tensile strength for trebles, high elasticity for middle registers and high specific weight for basses.

Such a diversity could be achieved by the string makers of the time both by introducing new twisting techniques and by merely "chemical" means suited to increment, as much as possible, the acoustic disposition of natural material. Among this methods the use of aluminium salts (29) deserves mention, and above all, the sulphuration process, a millenary silk bleaching technique, also used by the anonymous Paduan string maker from the first half of the 17th century mentioned by Skippon (30), which seem to go well beyond the function of merely bleach the material, which is achieved in a matter of a few hours, any way. Instead the ancients kept this operation going for days, even; one could suppose a function similar to vulcanization of rubber, causing a loss of plastic properties in favour of elastic ones (31). A partial answer to this question will perhaps come from the results of chemical tests under way, which aim at verifying weather sulphur can actually fix itself into the collagen, the basic stuff of gut, thus building up disulphide links between the proteid filaments.