I would like to point out that when people use gut strings today they are using modern gut strings, not historically informed gut strings!
One common feature of old lute instruction books is the test to see if your strings are true. I don't think this is to see if they are subtly outs - as modern gut may be after playing for a while - this is to see if the string is complete junk! You see, in the old days, a string was made be assembling fibers of gut (from very young sheep) and these fibers have a natural taper, and being a natural substance, have irregularities. With a thick string meant for the low courses there would be many strands of gut fiber, and they would tend to average out, but a treble might be made of three strands of gut, and any irregularities in the strands would make themselves evident. The *Modern Gut* is ground to make it regular, round and smooth and the same diameter all along its length. You can buy a modern gut string and *expect* it to be true, and *expect* it to be the diameter that you want. In the old days you bought a lot of trebles and threw out a lot. The cost of strings was a significant factor back then. Since the grinding process cuts into the fibers that make a strand of gut, modern gut is probably weaker than then the old stuff. But in general the new stuff is truer. And it is unquestionably different! And not historical. Wayne See http://www.daniellarson.com/article.htm for a discussion of how modern gut strings are made. To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html