[musume_no_hoshi]

Ayako Kawasumi is a skilled pianist, and wrote the opening to Piano. Haruko Momoi plays the pianica and composes her own songs. Even the super-popular Nana Mizuki composed a couple of songs too, I don't remember reading anywhere that she knows any instruments well. I do find Super Generation by Nana Mizuki pretty good. From Mayaa Sakamoto recent concert tour, she seems to know how to play the piano pretty well too.

Hirano Aya should just practice singing before learning any instruments...-cough-

I was thinking the same thing, I couldn't find in the jackets who played the instruments in the song. From other jackets I seen before, they credit the people that played them. I thought the song writers aren't found by the animators but by the production company? Althought KyoAni has a good track record of finding good unknown seiyuu.