Here's how it works. You enter in a song or an artist, and it creates a radio station based around the musical qualities of that song or artist. This process uses the Music Genome Project, which is totally sweet. You can "seed" as many songs/artists as you like. Then, when it's playing songs, you can give them a "thumbs up" or a "thumbs down". It's pretty intuitive, but the FAQ is very thorough in case you want to know exactly what thumbs up/down does to a song.
I have the following stations, all made by me (seeds in parentheses):
- Chill male alternative (John Meyer, Modest Mouse, Barenaked Ladies)
- Celtic punk rock (Flogging Molly)
- Reggaeton 'n' Rap (Gasolina by Daddy Yankee)
- Soul of Pop (Boyz II Men, Told You So by BNL, More Than Words by Extreme, At This Moment by Billy Vera & The Beaters)
- [Dude] thinks it's cool (At The Drive-In) [my station for my ex-Dude]
- I can dance to it (Single Ladies by Beyonce, Live Your Life by T.I., Crank That by Soulja Boy)
- Pseudo-psychedelic (Buffalo Springfield, The Yardbirds, Syd Barrett)
- Kinda Folky (Blackbird by The Beatles)
One caveat: Your seeds are used individually to generate your music. So if you type in "The Beatles", it really seems like the songs generated could have the musical qualities of any Beatles song ever. So if you seed a lot of artists, you're going to have to thumbs-down a lot of crap.
When you thumbs-down a song, normally it will skip the rest of it. But you only get six 'skips' an hour per station. Especially when you're first making a station, you might thumbs-down a song and have to suffer through the remainder of it.
But as faults, those are extremely minor. It's free, you get to make as many stations as you can stand, and each station is completely customizable. So, all in all, a great service. If I were you, I'd get an account while it's still free. (If you were me, you'd already have one, because I do. And that's how these things work.)