This is starting to look more interesting! I synthesized some drum kit sounds as well. I created new buttons for it, and now you can use both bass and drums to make a music loop.
Of course, having the icons stacked on top of each other is really confusing. The next step would be to implement a "layer" system of sorts, to show only one instrument at a time. And a delete button as well!
The bad news is that July's ending and I'm really running out of time for this. I don't think I'll have time to implement the "game" part of this, and will end up "only" with a toy, in the game design terminology –i.e. something that is fun to play with, but does not have victory or lose conditions. There are some popular games that fit the "toy" category, like The Sims, so I'm definitely counting this for the purpose of the project: 6 games in 6 months ;)