Oh sorry duckfromdisk, you did indeed say acousticbrainz! Yeah mood extraction would be the dream, but MeB got pretty burnt by AcousticBrainz. If anybody ever came up with a good, open source, system I don't see why we couldn't integrate it though
I wonder what kind of analysis Spotify does. They have such a lot of user data that they might not even lean on it that heavily. If anyone has any articles I'd be interested