basics to identify note timings in audio track

Hi..

I was wanting to experiment with identifying the time at which notes are played from an audio file. This will be on a drum kit with a multi mic-setup... each drum individually mic'd.

I figure I'd start w/ just Snare and Kick tracks..

The ultimate goal is to provide near real-time feedback on how off grid the playing is..

Thx in advance for any tips on what I could/should be looking at within the M4L toolset to create such a device.

Thanks!