https://github.com/adamstark/Chord-Detector-and-Chromagram

This library is real-time and performs well enough to play along.

Usage with JACK Audio Connection Kit can be seen here: https://github.com/relascope/chordola

@herzmeister: the guys from melodyne don't talk much, but I think they are using the stuff from the experience around Sonic-Visualizer and Tony (https://sonicvisualiser.org/tony/)