After overtures of an imminent American launch last week, the music streaming site Spotify officially launched in the U.S. today after finalizing a deal with Warner Music Group late Wednesday, reports Billboard. The service is being offered in free and paid premium versions; if you're willing to pony up $4.99 per month for the Premium service or $9.99 per month for the Unlimited service, you can join up immediately. But free-loaders are going to have to wait for a special invitation. (The free service also comes with ads and restrictions such as limited streaming hours.) Spotify is said to be offering more than 15 million songs.