Something that came into mind was how artists can play an instrument and sing at the same time. Would it be possible to consider implementing something similar to this in game for bards, increasing the difficulty of playing an instrument and improving how much performance you gain per pulse.

Play concerto
>You begin a quiet concerto on your blackened zills, your skill in your craft showcased in every note.

Sing melody/chorus
>You sing an beautifully operatic melody to accompany the concerto you're playing. The sounds melding in a masterful harmony of tone, tempo and melody.

again, just a thought.