It ran on windows 95 or 98 I believe. It allowed you to make music by placing colored blocks in various rows. I think it was associated with mtv, but I'm not sure (I had never actually heard of MTV at the time I had this program). It also had an odd feature where you could make music videos made up of moving geometric shapes. One of the sample songs, which was some kind of rock/metal thing if I remember right, featured a green box 'inflating' in time to the music.
What program was this?
edit: It looks like the MTV music generator from Jester Interactive released in 2000, however, that was a ps1 game. I played this on the computer if I remember right.