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. Note to x86_64 users: if your VAMP host application can't seem to find the plugins, you may have to 'export VAMP_PATH=/usr/lib64/vamp'. The SBo vamp-plugin-sdk (v2.1, build 2) package at the time of this writing still defaults to using /usr/lib/vamp. Future builds of vamp-plugin-sdk should address this.