I had a lesson with baroque violinist Stefano Montanari today, and he stretched animal intestines across my violin when I had finished. This was a compliment.
Baroque violins are different from modern instruments in several respects, one of the most important of which is the strings, which are traditionally made of cat-gut instead of metal/synthetic blends.
Stefano Montanari's violin, a 1680 Hendrick Jakobfz
They are also tuned a half-step lower than modern instruments, which is a problem when you have perfect pitch and are given an opportunity to play an audition with baroque tuning, on one day’s notice. I’m afraid my neighbors didn’t appreciate my dogged attempts to adjust to the new tuning, which must have resembled some of the sounds made by the unfortunate creature whose guts now decorate my instrument.
By this morning, I had reduced the number of times I hit an A# when I wanted an A to a just-above-reasonable level, and managed to get through a couple movements of Bach for Maestro Montanari well enough for him to ask me to join his class (on the condition that I change my strings to gut). So now I have a day to play around with my brand-new setup, and hope that I don’t get gutted by my neighbors for trying.
) 
I’m so glad that you had this opportunity and it’s clear that Signore Montanari appreciates your talent. Brava!
Guts?! I love your playing…it makes me feel very peaceful!