Digital radio listeners will soon be able to instantly buy tracks they have listened to.

The chief executive of radio company UBC Media , Simon Cole, revealed the service would be launched in London very early in 2007, rolling out across the UK by May. The technology is known as Digital Music Downloading (DMD).

UBC ran a successful trial in August with Birmingham's Heart FM 100.7.

Heart is a Chrysalis -owned station, and UBC says it has reached agreement with the company to roll out DMD over Heart and one other station.

Other stations will also be taking part, including Smash Hits and The Hits from Emap, Smooth from the Guardian Media Group and UBC's Classic Gold Digital, which it part-owns with GCap .

Limited by bandwidth

To facilitate the service, UBC has reached agreement with three major record groups: Universal Music Group, Warner Music and EMI.

A statement from UBC explains why the initial station line up is fairly restricted: "The initial line-up is limited by the current availability of data capacity to carry the music files on digital radio multiplexes."

A digital radio station multiplex is a group of DAB stations - for example the BBC 's National Stations sit on one multiplex, your local stations sit on another.

The original concept for the DMD technology involved the song being delivered to the radio itself, or to a mobile phone. However, UBC has also announced it has written a new version of the application for delivery over the internet.

"This new version of the application will allow exactly the same impulse purchase of songs as they are played," the statement says, "but with the music file being delivered to the user's home internet account rather than the radio itself.

"This requires minimal digital radio data capacity and it is therefore possible for it to be enabled on a far wider number of stations."

UBC was originally founded as one of Noel Edmonds' Unique-branded companies.

The presenter resigned from the group in March. Dan Grabham