[@CirusArvennicus]
I believe in a combination of both. The Vocal gem is just the emitter of power. I'd love to hear your idea of incorporating instruments.
My first thoughts would be summoning them as specialized weapons, and using them in concerts. They could even be a major attraction of an Idol. You could even branch some cool magical abilities from said instrument.

[@Fabricant451]
Yaaaasss~ Glad you're keen~