Couple Things
There should be no way that completing a song should not unlock the next song. I barely eeked out finishing the 3rd song, only to find out that I needed to do it again because I hadn't scored high enough.
My only other real complaint, is that if you're going to have multiple arrows at the same time, make multiple columns.
Could use a bit of work
While it's a nice concept, I noticed some things that aren't "bugs" but could be changed.
A) When you press down to make the blocks move down, you should be able to release it and have the block start moving at normal speed again.
B) The beat detector is unforgiving. It seems that if you aren't precisely on the beat, you don't hit it; no window for error. This is the kind of game where you get into a rhythm and once you miss one note, you're going to miss the next couple till you can adjust.
C) You shouldn't be able to go into negative points. Partially for the reason in B). If you miss one note when you're in a rhythm, you're going to miss the next few and you can end up digging yourself a hole before you even make a line.
Oh... and I gave you 10 for humour based solely on the fact the default name for the scoreboard was "Illiterate" and you spelt Rhythm wrong in the title.
A) yepp, that's how it is in normal tetris, but it wouldn't work when you only can press 'on beat'. New game, new rules.
B) All too true. Although "precisely" is kind relative, what would be the point if you didn't have to stay on beat?
C) That's noted, it might be too large a deduction. I had to put it in because otherwise the player can just spam the controls and not be on beat at all.
Oh) Now that's humor :D. I realised I spelt rhythm wrong when I uploaded it to newgrounds but I couldn't be bothered. I'm not native english speaker and can't see why anyone would want more that one 'h' in any word ^^.
Age 36, Male
Student
Canada
Joined on 6/15/07
Riff Off 
Rythm Tetris