The actual making of experimental loaded gut strings (32) went through a complex phase of quality standardization, which also included a careful study of treatises about dyeing and tanning of leather in use in the 16th and 17th centuries (33) and a long experimentation, through a some hundreds of tests, with such ancient dyeing and tanning baths (but obviously avoiding any toxic product). These experiments allowed us to discover the peculiar characteristics of the new strings, which could be then related to the historic information in our possession.

The specific weight reached was about 2.90 , i.e. 2.3 times the density of plain gut which corresponds to a diameter 34% smaller than plain gut strings and 40% smaller than rope-construction strings, thus perfectly compatible with what was measured on the bridges of the examined historic instruments.

The tone of the so obtained strings, as was to be expected, was rather dark, fundamental-heavy, bringing back to mind the only record in our possession by the English poet Edward Benlowes (1603-76), of how bass strings of the past might sound (34). A tone, in short, lacking a good part of the higher harmonics, which was to be made up for, at least as far as the lute is concerned, by the use of octave strings. It was however perfectly coherent with the "personality" of the higher untreated gut strings, achieving a natural extension towards the bass, unlike what unfortunately happens with overspun strings, which from the very outset suffered from serious tonal dishomogeneity (35).

The smaller diameters (especially those smaller than 1.0 mm) showed, on the other hand, such a harmonics rich tonal response as to dispense with the need, for the lutes 4th 5th and 6th courses, for octave strings, in favour of a unison arrangement. It is curiously significant to notice how the use of stringing these courses with unisons began to spread roughly at the same time the custom of tuning the 7th course a fourth below the 6th came into use, and more in general, with the extension towards the bass in the late 16th century, first hints probably of a the availability of a new type of string. An iconographic hint to this may perhaps be found on the 7 courses lute in Caravaggio's "I musici", c. 1594-6 in the Metropolitan Museum of New York, where only the 7th course is a vaguely reddish colour.

Where extended neck come into play, owing to the reduced diameters, a rather bright and persistent sonority was achieved, enough, that is, to cause the problems the Mary Burwell lute tutor's author complains about. The tone on the other hand, became rather nasal. Used as bass strings on neck of limited extension, such as an eleven course baroque lutes for instance, the sound acquired a certain dark gravity almost percussive, which coupled in a perfectly homogeneous manner to the sound of the octave, also made of gut.

Tests carried out on bowed instruments (violins, viola da gamba, violone and double bass) confirm essentially what already experimented with the lute, and suggested also to reduce, even substantially, the amount of loading for mid range strings (violin 3rd and gamba's 4th) which sounded too bright. It was not necessary on the other hand to change the working tension normally in use. The breaking point instead, because of the loading process, underwent a decrease of 20÷25% compared to that of untreated gut, a minor problem for low register strings, which work at only a fraction of their total tensile strength. Anyway, the acoustic features shown by these strings inevitably led us to reconsider, for bowed instruments, the criteria for post positioning, hairs breadth and tension and the type of bow to be used. For today lutenist, they dispense to constantly stopping overspun strings in order to avoid unwanted dissonances.