Pandora I had already briefly linked here before, but I only got around to trying it out myself today. Wow. Really brilliantly simple setup. And although I didn't directly expect it - it works. Ok, there is one problem with my music taste: the musicians have done very different things, so it's strongly dependent on the initial piece in which direction the service goes if I only enter one musician. Unfortunately, when searching for titles, there is often a "not found" as an answer (or only titles of the same name by other musicians - Black Moon by ELP, for example). But if the starting point is usable, it really continues very consistently afterwards - and many musicians are brought in whom I had never heard before (ok, from some I also don't want to hear anything in the future).
In any case, it's really more than just a toy - it's really fun to just let the station run. And as a registered user (optionally free with ads or paid without ads) you can configure up to 100 stations and build your own mood radio.