Composer and men in small room beginning to improvise (7)

I believe the answer is:

(Other definitions for corelli that I've seen before include "A mandolin-playing Captain", "Arcangelo --, Italian baroque composer", "Arcangelo, seventeenth to eighteenth century Italian composer, violinist", "Marie - - , romantic 17", "Captain -'s Mandolin (de Bernires)".)

I've seen this clue in The Telegraph.