Magic music scrolls and bard buffs have always stacked. They just can't be 'played' at the same time.
1. Activate the bard buff
2. Cancel bard skill
3. Start the score with normal Playing Instrument
4. ???
5. Profit.
I know, thank you.
But, that alternative is really annoying to do when you need to have a somewhat perfect performance with just a berserk scroll. The side-effect from some magic scrolls just doesn't seem worth it [to play a skill buff and a scroll buff]. What I want is to have them buff at the same time while using only one skill, not after a skill buff and 1~5 attempts at a magic music scroll buff.