Piano Pitch Detection

This is a great problem, and hard of course (many
a PhD dissertation has been spent trying to solve
the automatic music transcription problem).

Having a known instrument is certainly a good start
and advantage.

First come up with your own ideas and schemes for
doing this task.  Then at some point check out Harvey 
Thornburg and Randall Leistekow's work on piano 
transcription.  The math is mega-gnarly, but this
represents the state of the art in piano transcription.

Also see Ansi Klapuri's work on polyphonic transcription.
Speaking of that, having dry recordings (no reverb) can
really help things out.

Forge Ahead!!