these are the ones i've read. just refer to the tags and the reviews i made
http://www.mangago.me/people/tag/49344/music/
Classical music:
http://www.mangago.me/read-manga/sore_wa_isshun_no_hikari_dewanaku/
http://www.mangago.me/read-manga/transfigured_night/ <3
http://www.mangago.me/read-manga/ano_kado_wo_magatta_tokoro/
http://www.mangago.me/read-manga/kimi_no_iru_sekai_shikairanai/ ch.4
http://www.mangago.me/read-manga/ludwig_ii/
Yaoi that involved with music??