The hashing algorithm is provided by Echonest in their Echoprint service and used to compare against their database (hopefully growing after their Spotify acqui

The hashing algorithm is provided by Echonest in their Echoprint service and used to compare against their database (hopefully growing after their Spotify acquisition). However before this can be done, the individual tracks have to picked out - I've not had much luck with Echoprint identifying more than one track at a time. Python, RQ / Redis for the task queue, RethinkDB for the backend, FFmpeg for transcoding and C for DSP (only in testing).