It's not difficult to detect all the notes via FFT, slightly more difficult to detect only bass notes (harmonics come into play), and quite a bit more difficult

It's not difficult to detect all the notes via FFT, slightly more difficult to detect only bass notes (harmonics come into play), and quite a bit more difficult to pull useful chords out. That said, my first Mac app, FuzzMeasure, is an audio analysis tool---so I know my way around the FFT/etc. Read into this comment however you please. ;)