It is Spectral Modeling Synthesis sms-tools of MTG UPF (Music Technology Group, Universitat Pompeu Fabra, Barcelona), by Prof. Xavier Serra (also as instructor in the Audio Signal Processing for Music Applications, Coursera).
http://mtg.upf.edu/technologies/sms
https://github.com/MTG/sms-tools
https://github.com/MTG/essentia
Several simple experiments I made.