Why has no one commented on this yet? 🤨 I'm not familiar with Sweet or Music Meister but given that they're from Buffy and Batman: the Brave and the Bold, respectively, they can't be that obscure.
Anyways, great set-up, broadway. Involving Lin-Manuel Miranda and wife (not to mention bringing up that Lin's an Oscar away from EGOT status), involving Neil Patrick Harris (who I just found out is Music Meister's VA, who in turned hypnotizes him) ... you've loaded this thing with easter eggs. Not to mention how funny this is with the back-and-forth with Lin and his agent and the musical duel between Sweet and Music Meister themselves.
As for the match, from a glance I'm inclined to believe that Sweet would have more powerful control over victims than Music Meister, so he'd probably win this head-to-head.