(CNN) -- A pioneer in sales of digital music, Apple on Monday became a late entrant in the booming music-streaming wars. When its iTunes Radio feature launches this fall along with a new version of Apple's mobile operating system, it will go head-to-head with established competitors such as Pandora and Rdio, as well as other tech heavyweights in Facebook-affiliated Spotify, Twitter Music and Google Play All Access. All of which raises the question: In a crowded field, what's going to persuade people already using (and, in some cases, paying for) those other services to switch to Apple's? Apple appears to be banking on the extensive music library it's piled up on iTunes and the customer base that's already used to shopping there. The iTunes store boasts a catalog of 26 million songs (Spotify, by way of comparison, claims more than 20 million) and more than 50 billion files have been downloaded from iTunes since it launched in 2001.
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Apple's iTunes Radio joins crowded music-streaming field
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Feature will be ad-supported, feature iTunes' 26 million songs
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Some question whether there's a need for more streaming
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Facebook, Google, Twitter and others already have services
Like @placeholder, users will be able to "seed" stations with particular artists and hear selections from similar ones.