Advertising industry site AdAge reports that major companies including McDonald's, Pepsi, Nissan and Procter & Gamble have signed up to 12-month campaigns worth "millions of dollars".
The ads are due to run across iPhones, iPads, computers with iTunes and on Apple TV set-top boxes, with listeners played one audio ad every 15 minutes and one video ad every hour. However, iTunes Radio will be ad-free for customers who pay for Apple's iTunes Match music service (£22/year in the UK).
Initially iTunes Radio will only be available in the US, although it is expected to be rolled out in other countries including the UK in due course.
It is not a direct competitor for the likes of Spotify and Deezer. Rather, it will feature more than 200 stations and a catalogue of music from the iTunes store.
There will be Featured stations curated by Apple and genre-focused stations personalised for each user. iTunes Radio evolves the more music you play and download from iTunes – in effect it learns your musical preferences.
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By Andy Clough