Seems like the person in question re-invented "NNLS chroma" or "Harmonic Pitch Class Profiles", which are often used for automatic chord transcription and relat

Seems like the person in question re-invented "NNLS chroma" or "Harmonic Pitch Class Profiles", which are often used for automatic chord transcription and related tasks. See, for example: http://isophonics.net/nnls-chroma http://isophonics.net/nnls-chroma or https://www.upf.edu/web/mtg/hpc https://www.upf.edu/web/mtg/hpc