Honestly not sure since I don't know which APIs + secret sauce they put into Song Radio. I personally found Song Radio a little lacking - I never usually liked the most of the related songs, it didn't allow me to reshuffle the recommendations.

The /recommend API I wrapped for the site is similar, in that I let it spit out 12 "similar" songs, but I'll probably only like one or two songs, but you can also re-submit to shuffle the recommendations. The site is definitely more for active discovery than passively listening. I made the site because:

1. I wanted to more actively discover songs

2. I'm a big Spotify fan and was curious about the guts of the recommendations algorithm

3. I had never deployed an actual site (I exclusively do backend programming at work) so it was good learning experience about things like setting up a little static site