Street Fighter X Mega Man has some pretty nice tunes, don't you think? As it turns out, there's also some unused pieces, too. The game's composer, ARival, uploaded one such track to his Sound Cloud. This piece was originally composed for Yang's stage, but was scrapped when Chun-Li became the preferred character during development.
Because this is labeled "unused track #1", we can probably expect to hear more stuff from the cutting room in due time. Bring it on!