young geniuses..
man, i can't even play the piano

Japanese people don't count. They're cyborgs with programming and scripting, and hacks.

I actually learned Iron Man on the guitar. Well, some of it.
My father's somewhat of a guitar prodigy so I tried the guitar, too. I ended up mostly dawdling a lot and never got very good. It's still fun to play, though.

It's good for kids. You practise manual skills long enough and you can do anything, especially if you're well suited to it for some reason- in those kid's cases: good coordination, dexterity, and good hearing.

Nothing of genius anywhere in the mix. It's not needed. Just application and time. It's a good thing they spent it playing musical instruments and not video games. ;)

ozoneocean
It's good for kids. You practise manual skills long enough and you can do anything, especially if you're well suited to it for some reason- in those kid's cases: good coordination, dexterity, and good hearing.

I don't know about good hearing. Playing next to those loud speakers again and again causes hearing to suck.

They may gain a sharper perception or sound distinction ability, but hearing will probably overall deteriorate.