Damn, that is a profound question! I eagerly await the revelation of the answer, for it is beyond me, oh wise one.

Are we talking about music as a singular thing or as a total entity?

If it's singular then I can picture notes falling from the sky, and symphonies sprouting up, requiems even.

If it's music as a total entity then the growth depends on amount, type, and the like. Music would spawn smiles, contentment, relief, inspiration, calm, rage, things of this nature. Much like the different storms we encounter, the different music would affect our world in so many ways. Some rain is gentle, some is torrential, these are the rains that can encourage delicate growth or destroy it while it nourishes more hardy stock.

Indeed, what would grow if it rained music?

I'm really glad you asked that, my mind is reeling now, and I have some really cool pictures running through my mind courtesy of my imagination.

Um...pot?

Notes would grow, and reproduce more notes.

I can hear the colors, man!

Wouldnt that depend on the music?

some badass vegetables man

Easy: Milksteak.

souls - music grows souls

Mostly corn for mass consumption but there would be gardens of amazing plants no one has ever seen before in strange places.

Anything and everything would grow. Music is so varied that if it were to rain "Music", the end result would be a non conformist crop of everything and the kitchen sink. I say this because I like mostly everything. Another person might like R&B but also some random country. People like randomness these days....

And as much as I hate maintstream garbage, I don't know of anyone that likes nothing but what the radio tells them to listen to....

Different combinations and remixes of all the music that poured into the ground.

Bluegrass of course.

Notepaper.

a David Lee Roth tree?