The 30-second ads began appearing last week when users listen to songs on artist profiles, album pages, playlists and pop-out players. They expand on a trial that began in December.

The ads are impossible to avoid, unlike the visual ads that can be put out of sight in background windows as users listen along while doing other computer work.

But the audio ads are timed so that a user can listen to up to 100 songs on a playlist or to a full album with just a single interruption after the first song.

MySpace Music is a joint venture between major recording companies and News Corp.