With some work, could be a great music game.
First off, I gotta say it reminds me of Amplitude, which I loved.
Anyways! I gotta say, the game was quite addicting after I played it once. It's really quite a pain in the ass to try and hit all the chords individually (Since you know, I just resorted to holding all 4 down LOL) but it adds some difficulty to the game. Granted, I never got past the first song, but from what I already heard I can definately say that it's at least on a good wavelength.
So yeah, definately try and tweak the gameplay a little bit, and maybe start off with some easier chords, and the game will be excellent.