We've been working away on a few things here, one of which is another entry into the music category. Like FourTrack, Doppler (working title) is a portable music sketchpad for your iPhone or iPod touch, but that's pretty much where the similarities end. While FourTrack is a tool for recording your instruments, Doppler is itself an instrument. At its heart, is a very capable synthesizer, sampler, and loop-builder - all controlled with a fun touch interface.
Here's a little peek at an early build:
There's a longer version, with a more detailed description of the various screens at youtube.