Yes but if you get +15 music buff from singing anyway, the upgrades on instruments become moot.
Only thing saving instruments is ironically cash shop reforges.
But singing at rank 1 adds 15 buff which is already more than what an instrument can add without reforges, and the mic is also upgradeable and i believe reforgeable.
Again... what Kenero said.
Singing gives +15 music buff at rank 1 because it does not gain any bonus from playing instrument.
Playing instrument gives +15 music buff at r1 is why singing gives +15 music buff at rank 1.
So people who play with the instruments/mucs will always be better than the ones who just simply sing with any other weapons, not using instruments/mics.