OCR for piano recordings.
Every now and then a startup appears which really has thought about their business model instead of just making something and trying to sell it afterwards. The guys at Zenph Studios cleary has one of those million dollar moments when they came up with the idea which would be their future business model.
Zenph has created technology which can essentially listen to old low quality (audio-wise) piano recordings, and recreate those performances on a digitally controlled grand piano. The result: a pristine quality piano recording which sounds exactly the same as the original, except for the vastly improved audio quality. I find it very exciting that computers and signal processing are now approaching a level where it's possible for computers to "listen" to something and actually being able to extract the various elements of a piece of music. Once this becomes affordable it will open up lots of interesting possibilities... imagine being able to use old (no longer copyrighted) recordings to extract riffs and solos, not just as static samples but as notes that can be edited further.
More on the technology at pragmaticprogrammer.com: A Pragmatic Project: Live In Concert. Stumbled upon via Slashdot.