But does it tell you that YOU ROCK! if you get most of the notes right?

I think the problem of encoding the analog signal as midi data is pretty much solved for the guitar. I've found the terratec axon guitar->midi system great in terms of accuracy and latency between striking the note and hearing the MIDI sound. It (supposedly) uses a neural net to learn the sounds your pick makes hitting the different strings when depressed at different frets. These sounds are slightly different from each other, so it can tell from the attack alone (no waiting for complete cycles of the fundamental) what note you are playing. I