Here is what I've been working on for the past year:

It's a Game Boy song editor for creating original songs for Pokemon Gold, Silver, and Crystal.
Source code is on github: https://github.com/dannye/crystal-tracker
Big thanks to Saga Musix and manx for answering my technical questions here on the forums when I needed help.
A YouTube playlist showing off how it looks and sounds:
https://youtube.com/playlist?list=PLID18C84BACW1CIG9L1OUtmtSiUSRmuA5
Impressive, certainly not what I expected to be result of your questions. ;)
Next I gotta figure out how to emulate the drum instruments... Been putting that off this whole time.
Drum instruments are in!
https://www.youtube.com/watch?v=9ajQO5ySRRU
https://www.youtube.com/playlist?list=PLID18C84BACWAGZ3RBXtws0tBFvsGoCmI