I made this drum machine with Cocoa. You can edit your loops in a text editor. I made it because I like the idea of using text editors (specifically TextMate) and not point-click interfaces like Garage Band.
It "works" in that I can demo it, but I need some help from an expert at Core Audio to make it really work. Right now there's a few problems with timing that I can't get past given my nearly complete ignorance of the subject.
If you know anyone that can help me, I'd appreciate it if you sent them my address: andre at torrez.org.