Here's how it stacks up to its closest competitors.
Spotify: This European service has grabbed up customers since launching in the U.S. in 2011. Users have the ability to pick and choose the songs they want to listen to from the service's vast catalog. Spotify users can compile and share playlists on their computers for free, as long as they put up with the occasional ad; mobile devices only allow them to play Internet radio stations unless they subscribe to the company's premium service. Spotify subscriptions start at $10 per month, which eliminates ads and lifts those restrictions on mobile users.
Pandora: Pandora uses the "Internet radio station" model, allowing users to create stations based on songs or artists they like -- "The Rolling Stones," say, or "All About That Bass" -- and uses an algorithm to pick other songs like it. The service is free, with ads. Users can pay $5 per month to skip those ads. On Pandora, users don't buy (and therefore don't own) individual tracks.
Google Music: This $10 per month service lets you listen to music you've purchased through Google Play, with access to your personal playlists, as well as online radio stations and playlists recommended by Google Music itself. A subscription also includes access to the beta of YouTube Music Key, which gives you ad-free access to select music videos online or off.
Amazon Prime Music: Amazon Prime Music allows you to listen to music you've purchased through Amazon from your computer or mobile device, as well as to certain tracks deemed part of the Prime catalog, for free. It also offers playlist suggestions and is part of the company's $99 per year Prime shipping, media and storage service.
Tidal: Owned by a host of famous artists -- notably rapper Jay-Z -- this music service attempts to trade on star power as well. It also claims that the quality of its streams outstrip the competition. Tidal has no free tier; standard streaming costs $10, while users can also opt to pay $20 for high-fidelity sound. The launch has been deemed rocky by many in the tech and music industry, who say that the service may not offer enough to overcome the fact that it has no free, ad-supported option.