As I'm away this weekend, and Prop and Bat are busy with things, I thought I'd show you what I've been working on lately.
It's a rhythm game, in the Guitar Hero style, and it's tentatively called Waveform Hero.

This is part of my university coursework: a collaborative project. I'm counting it as collaboratve because I'm reusing Battery's Widgets code form TurnShip, among other things. It'll use Guitar Hero controllers.

You are this little waveform (or "Melody Snake", as it was known earlier on); you use the guitar frets to move him between the lines of the stave, and strum like GH.
The whammy bar will be used to change his waveform between square, sine and triangle waves, although I haven't tested this and it might be difficult to do while playing.
I'm using a keyboard at the moment. ASDFG for the frets, W to change wave, L to strum.

The idea is to collect blocks that are the same shape as your waveform, and as you go over a block, you make a note. I can lead the player to making particular melodies this way. You'll be able to make sounds even when not on a block, unlike GH.
I also like the idea of having to avoid percussion, but I'm not sure if that will stay in the final version. I did this concept at the start of October and things have changed a bit in my head since then.
If all goes to plan with this, it might actually end up released before TurnShip, which would be... embarrassing. But this game is a lot simpler, anyway.