Last.fm are perhaps the most successful discovery-mainly service. They had a ‘radio’ thing with a licensed catalog, but apparently finally dropped it in 2014. Otherwise, they are somehow chugging along for almost twenty years. However, I don't know how well their finances are, lately. The service doesn't seem popular in the past ten years or so, and I myself have just drifted away (in favor of less predictable and comfortable discovery by chance or by research, actually).