nnls-chroma is an open source Vamp plugin library for harmony and chord
extraction with some features aimed at amateur musicians, and some at
music information retrieval researchers.  It contains the Chordino,
NNLS Chroma and Tuning plugins described below. Their main features are:

* Chordino: a simple, no frills chord transcription method based on NNLS
Chroma features,
* NNLS Chroma: high-quality chroma features for harmony visualisation
or further processing,
* Tuning: an estimate of the 'concert pitch' tuning.