Spotify is planning to introduce a free mobile version of its streaming music service, according to The Wall Street Journal. The free version is said to be ad-supported and focused around playing personalized radio like Pandora or Rdio's Stations feature, though users will also be able to play a limited number of songs on demand — it's otherwise unclear how the free tier will differ from the existing Radio feature. Spotify's current on-demand mobile service is only available to premium subscribers, with its free version restricted to PCs.

Spotify has wrapped up deals with Sony, Universal, and Warner for the free service, says the Journal; at issue were the rates the company would pay the label and the level of on-demand control users would have. The service could be announced as soon as next week at a Spotify event in New York City.