It begins when the user visits the site. Pandora asks the user to name an artist or song that he or she likes. You can then “save” the station for later playback.
Pandora gives the option for you to leave feedback, at which point it will adjust the song selection based on your feedback. They also allow the user to enter multiple songs/artists.
All it takes is one song name to get started. It will automatically generate a custom radio station for you with just that!
Pandora bases their artificial intelligence on the Music Genome Project. The project’s website says it best:
Together we set out to capture the essence of music at the most fundamental level. We ended up assembling literally hundreds of musical attributes or “genes” into a very large Music Genome. Taken together these genes capture the unique and magical musical identity of a song – everything from melody, harmony and rhythm, to instrumentation, orchestration, arrangement, lyrics, and of course the rich world of singing and vocal harmony. It’s not about what a band looks like, or what genre they supposedly belong to, or about who buys their records – it’s about what each individual song sounds like.
To make things more convenient, Pandora.com is the “squeezebox.” It is a device that can play your Pandora radio through your stereo.
LifeHacker has a great article on getting the most of this new free music service. I would strongly recommend you check out their article.
Also, tailwind blog has a review of several music services such as Pandora, Last.FM, and Mog.