[drewcrawford]

Forgot about Live. Supports VST and AU (mac version only).

At any rate, my argument was (although I didn't explicitly lay it out) that he should cover AU for the garageband kids (bulk of the users) and the actual musicians that use Logic at band practice (sizable minority), and maybe catch VSTs on the way out for the Windows folks if it's not too hard (I'm not a VST developer; I can't say). AU is where it's all going though--you've got a generation of people growing up with garageband for recording, producing, even taking piano lessons. I would imagine that would be prime market for a chord detection app. In addition, the GB/Logic family file format is based around chord notation (and is pretty easy to reverse engineer), so you could actually export the chord structure back into the arrangement if you were clever. This has all sorts of interesting implications for chord-aware events like Apple Loops-- mixing would be drag and drop even for the people who don't know one chord from another.

Agree that Pro Tools isn't much use for this sort of thing. I do know a couple of kids who've picked up Pro Tools LE because they think it's what the cool kids use, but it's not worth the effort to capture.

Another obvious direction for this would be an iPhone app that displays the chord it currently hears (and does so accurately). Not sure how good the algorithm is from a bad source, but that would be worth $50 to me.