What you've described is a Very Hard problem. :) Dozens of researchers around the world are trying to tackle it, with varying results. Piano is actually one of

What you've described is a Very Hard problem. :) Dozens of researchers around the world are trying to tackle it, with varying results. Piano is actually one of the easier instruments to automatically transcribe, in part because the notes decay in a predictable way and there's (generally!) no vibrato or changes in tone once a note has been struck. Unlike, say, a clarinet or a guitar, where pitches can be bent after the initial note onset. Context: I run Soundslice (http://www.soundslice.com/ http://www.soundslice.com/), an interactive sheet-music site, and I've investigated this deeply over the last few years.