You also won't be able to avoid radio ads in between certain songs. The advertising on the side of the Pandora app can be annoying.
If you don't like the music comes up on your station, just click the thumbs down button and the app will take that into consideration for future suggestions. You can create stations based on a song, music genre, or specific artist. If you do want to register and have Pandora remember your music preferences, the process is free and simple. You must also be located in the United States to use the service however. Unlike the web-based version, the Pandora Pokki app doesn't require you to create an account to enjoy music from your desktop. Using the Music Genome Project, Pandora will analyze the musical content of the song or artist you vote that you like, and it will play other music that shares some of the defining qualities.