Aubio is a library for audio labelling.  Its features include segmenting a
sound file before each of its attacks, performing pitch detection, tapping
the beat, and producing midi streams from live audio.  The name aubio comes
from 'audio' with a typo: several transcription errors are likely to be
found in the results too.

The aim of this project is to provide these automatic labelling features to
other audio software.  Functions can be used offline in sound editors and
software samplers, or online in audio effects and virtual instruments.

WWW: http://aubio.org/