Pathetic reaction time!
Don't get me wrong here - the game looks great, and I'm sure it could be a very good replica of the real GH games. But you only get about half a second to react to each note as it appears!!
How are you supposed to hit everything when you barely have a chance to see it?! The real game gives you MUCH more time when you can see the notes before having to play them!
Also, just like the real GH games, you should not include the number 5 key on the easy songs. You should start off by possibly just using 1,2,3, then introduce 4, then definitely only introduce 5 after a few simple songs.
Unfortunately, I got fed up and quit after just one song because of the terrible gameplay - but I'd definitely want to give it another shot if you bother to update it a bit.
By the way, I didn't fail at this game simply because I'm rubbish at it - I've completed many other GH-style games on here such as the SCGM series with all perfects. It was your gameplay that's the problem.