I think Patrick O'Brian's The Ionian Mission might be the best of his historical fiction series. While Stephen is on a spying mission in Spain, here's Jack with his violin with something baroque:
Now when the fiddle sang at all it sang alone: but since Stephen's departure he had rarely been in a mood for music and in any case the partita he was now engaged upon, one of the manuscripts he had bought in London, grew more and more strange the deeper he went into it. The opening movements were full of technical difficulties and he doubted he would ever be able to do them anything like justice, but it was the great chaconne which followed that really dsturbed him. On the face of it, the statements made in the beginning were clear enough; their closely-argued variations, though complex, could certainly followed with full acceptation, and they were not particularly hard to play; yet, at one point, after a curiously insistent repetition of the second point, the rhythm changed and with it the whole logic of the discourse. There was something dangerous about what followed, something not unlike the edge of madness or at least of a nightmare; and although Jack recognized that the whole sonata and particularly the chaconne was a most impressive composition he felt that if he were to go on playing it with all his heart it might lead him to very strange regions indeed...
