Unfortunately after a while they restricted access to US listeners only. So if you're reading this in the UK and you follow the link above you'll get a 'restricted' message. To reach it you need a proxy service in the US. Here is their description of themselves ...
About Pandora®When was the last time you fell in love with a new artist or song?
At Pandora, we have a single mission: To play only music you'll love.
To understand just how we do this, and why we think we do it really, really well, you need to know about the Music Genome Project®.
Since we started back in 2000, we have been hard at work on the Music Genome Project. It's the most comprehensive analysis of music ever undertaken. Together our team of fifty musician-analysts has been listening to music, one song at a time, studying and collecting literally hundreds of musical details on every song. It takes 20-30 minutes per song to capture all of the little details that give each recording its magical sound - melody, harmony, instrumentation, rhythm, vocals, lyrics ... and more - close to 400 attributes! We continue this work every day to keep up with the incredible flow of great new music coming from studios, stadiums and garages around the country.
With Pandora you can explore this vast trove of music to your heart's content. Just drop the name of one of your favorite songs or artists into Pandora and let the Genome Project go. It will quickly scan its entire world of analyzed music, almost a century of popular recordings - new and old, well known and completely obscure - to find songs with interesting musical similarities to your choice. Then sit back and enjoy as it creates a listening experience full of current and soon-to-be favorite songs for you.
You can create up to 100 unique "stations." And you can even refine them. If it's not quite right you can tell it so and it will get better for you.
The Music Genome Project was founded by musicians and music-lovers. We believe in the value of music and have a profound respect for those who create it. We like all kinds of music, from the most obtuse bebop, to the most tripped-out drum n bass, to the simplest catchy pop tune. Our mission is to help you connect with the music YOU like.
We hope you enjoy the experience! About Our Name
So when Spotify www.spotify.com appeared in the UK I was ready to participate. But actually it is not so smart, and those advertisements which seemed louder than the music made it a little-used icon on the desktop.
Last spring I was in Sweden, looking through a friends music collection for some unfamiliar music that I was about to see in concert. He didn't have it on CD or vinyl, but then produced his laptop and found it on Spotify. So far quite unremarkable. But then he streamed this to a device attached to his hifi. And because he had a Spotify subscription the quality was high and there was no advertisements!
Furthermore, music in Itunes on his laptop could be accessed directly, wirelessly from his hifi using this device which has a small touchscreen.
The device is called Sqeeezebox. ..... the seeds were sown!