None of Jim's "Art Renewal Center" links work. Here's one of the Leighton "Music Lesson" that does:

http://www.rbkc.gov.uk/leightonarabhall/paintings/enlarge/p13.html

The instrument is a fairly normal shape for a divan saz (the medium size) but he's got the strings wrong - should be three double (or double and triple) courses, instead he's painted it with six singles.

This one is interesting:

Performers from ancient Pompeii

Double shawm, crotals and frame drum. The drummer is using exactly the same technique as a modern Iranian or Kurdish daf player. Must have been a spectacularly energetic show.