Thank you for this kind feedback.
I'm glad to hear you're enjoying the game so far, and that you found the characters believable (and it's nice to hear Bastien getting some love, too - he does not seem as popular as some of the others ^_^)
As for the music, I am happy to say that it is, bar three tracks, all creative commons work and available to download for free .
The two Mozart pieces should be easy enough to google (Clarinet Concerto in A major, K. 622 - I. Allegro and Piano Concerto no. 10 in E flat major, K. 365/316a.)
As for the other tracks, they are by a talented and generous composer called Kevin MacLeod, and can be searched for here https://incompetech.com/music/
I think many people who make games (and youtube videos) use his work.
Tracks I used in this game are as follows, but I think the piece you might be referring to is "Trio for Piano, Cello, and Clarinet" or possibly "Heartbreaking".
"The Rule", "Sugar Plum Fairy", "Hidden Agenda", "Heartbreaking", "Reaching Out", "There is Romance", "Trio for Piano, Cello, and Clarinet",
Anyway, good luck in finding the track you were looking for (and possibly even more great music) on his site, and thank you for playing.