NNLS Chroma/Chordino 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.

If you'd like to understand chords and harmony better, then this NNLS Chroma library may be just what you want.

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.

If you want to start right away, you can download readily compiled binaries for Windows and Mac OSX (Intel) from here -- Then just use them in a host such as Sonic Visualiser or Audacity, which are also open source.

For the source code check the Repository tab.


A small selection of other projects in which NNLS Chroma/Chordino features


  • Last.fm use NNLS Chroma to enhance classification in their iPad app
  • Chordify performs chord recognition based on NNLS Chroma
  • McGill Billboard Project provides NNLS Chroma for all annotated tracks
  • Yanno uses Chordino as a chord extractor


  • de Haas, Bas, José Pedro Magalhães, and Frans Wiering. "Improving Audio Chord Transcription by Exploiting Harmonic and Metric Knowledge." ISMIR. 2012.
  • Baume, Chris. "Evaluation of Acoustic Features for Music Emotion Recognition." Audio Engineering Society Convention 134. Audio Engineering Society, 2013.

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Related publications

M. Mauch and S. Dixon, “Approximate Note Transcription for the Improved Identification of Difficult Chords,” in Proceedings of the 11th International Society for Music Information Retrieval Conference (ISMIR 2010), 2010.
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Manager: Chris Cannam, Matthias Mauch

Recent activity

2019-05-20 04:23 PM Chris Cannam
Revision 181:89099872c87b: Install Vamp SDK
2019-05-20 04:11 PM Chris Cannam
Revision 180:0a0884e29bc2: Add Boost
2019-05-20 04:05 PM Chris Cannam
Revision 179:ea0c7382705a: Fix package path
2019-05-20 03:56 PM Chris Cannam
Revision 178:ba78ca8cb956: First cut at a Travis build