This is very true. I'd pay for a metadata-only / playlist service that works with Spotify/Tidal/Apple/local music. And don't allow free-text tags. Instead you

This is very true. I'd pay for a metadata-only / playlist service that works with Spotify/Tidal/Apple/local music. And don't allow free-text tags. Instead you give a list of available tags - the lowest number needed to describe most tracks. I mean, let people add their own if they want, but you should ignore those while training the model. I actually think that instead of trying to tag some specific mood (eg "happy") some sounds be a sliding scale between two opposites: happy<-------|--->sad Instrument tags are easier to understand. Give a list of instruments (or instrument types, because the user might not know precisely which woodwind or percussion instrument it is) with checkboxes beside each. Some users will be experts because they play woodwind. Let those users apply to become experts, pass a test, "identify the instrument", and if they pass, give them half price subscription as long as they moderate X tunes per week.