A few suggestions to improve the game:
1. You could rearrange the block patterns to play a common musical phrase, (the first line of happy birthday for example) that would deal the maximum damage for any given level. It would help take the randomness out of the game and add an interesting puzzle aspect to the game.
2. It would also be nice to be able to play more than one cord per measure. Most songs don't stick to one cord per measure.
3. Add the seventh cords to allow complete cord progressions.
4. Add eighth notes and half note to give some flexibility to the composition.
5. add a level editor and sandbox mode. it would be fun to try and guess other peoples songs.
I know it can be difficult to program a game to include these elements, but I think it would make a good game truly awesome. I love the concept and the potential.
Its not the random music that does the damage, its using the blocks right. if you pay attention you will notice in the view screen the top half is labeled c2 through b2 and the bottom is c1 through b1. each letter has two columns, one for the natural (white key) and the other for the sharp (black key). to do the most damage include these notes in your composition. For best results play the notes corresponding to the blocks closest to the ghost spawn point first, then those going to the first star, then the spawn point to the second star etc. Repeat the notes close to the spawn point a first, then the ones toward the stars later in your composition.