Comment by dunk010

I worked at Last.fm from 2007 to 2012. The MIR team (think: research) developed a wonderful system called "RadioQL", which allowed you to stitch together custom ratio stations from any of a huge host of factors, joined together by AND, OR, and NOT. You could select artist radios, song radios, tags, and so on, but also combine this with things like the BPM or even some sentiment analysis. It was used a little bit inside some public-facing radio stations, but nobody outside of the staff ever got full access, and that's a tragedy as it was glorious.