Pandora grew out of the Music Genome Project. The idea with this project is that the system will monitor your likes and then create a custom station which will match those likes. In my testing it seems to work reasonable well. A nice thing about this website is that you can type in a music type as well as an artist and it will attempt to build a station to your likes. For example if you like Piano music, you can type in Piano and it will create a station of piano music. In some competing sites you would have to select a piano music composer in order to get the same result.