Spotify is reportedly set to launch a free, ad-supported version of its popular music streaming service on mobile devices.

That’s according to The Wall Street Journal, which, citing sources familiar with the matter, notes that Spotify has signed deals with Sony, Universal, and Warner for the new service:

Spotify, which has 6 million paying subscribers and 20 million active users world-wide, has been negotiating for nearly a year with the three major record companies— Sony Corp.’s Sony Music Entertainment, Vivendi SA’s Universal Music Group and Access Industries’ Warner Music Group—over the rates it will pay them to play songs on the free mobile service, and over how much direct control users have over what they listen to, these people said.

At the moment, a free version of Spotify’s music streaming service is available only on desktop. On mobile, Spotify’s service requires a premium subscription.

But with the launch of the new service in question, non-subscribers can enjoy ad-supported music streaming on mobile. The service is expected to allow a limited number of songs to be played on demand and to offer custom radio stations for the most part.

The new service may be announced next week in an event in New York, to which journalists have been invited by Spotify “promising doughnuts but divulging little about what the company planned to announce.”

Of course, it’s not unreasonable to assume that Spotify’s anticipated next big move has to do with iTunes Radio, Apple’s very own free, ad-supported music streaming service on mobile as well as desktop. With this move, Spotify follows Pandora and Rdio, two of its biggest rivals, in offering competitive free mobile listening.

A few weeks before the official launch of iTunes Radio last September, Pandora dropped its free mobile listening cap. And just a couple of months ago, Rdio launched free mobile listening for all stations.