LOS ANGELES (AP) - Hoping to boost revenue, MySpace Music has begun experimenting with audio advertisements that users must hear if they want to listen to music for free online.

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, banner ads that can be put out of sight in background windows as users listen along while doing other Web surfing or 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.

The oral pitches make online listening more like over-the-air radio, although online listeners can choose which songs they hear.

MySpace Music, a joint venture between major recording companies and News Corp., wants to boost the frequency of such ads this month before settling on how often they'll be running. Other online music sites such as Pandora and Yahoo Music already run similar audio ads.

"We're testing some new ad products and the response from our users has been positive," MySpace Music said in a statement. "As always, we are interested in hearing feedback from our users and advertising community as we run these tests."

Some early advertisers include TurboTax and Office Depot. The ads are sold by online audio ad company TargetSpot Inc.

News Corp. Chief Executive Rupert Murdoch said last week that MySpace's turnaround is "not yet where we want it." The company said its digital properties, including MySpace, experienced a fourth consecutive quarter of falling ad and search revenue.

MySpace is being overhauled by Owen Van Natta, a former Facebook executive who joined the company last April as its CEO. Once a leading social-networking site, MySpace has lost market share to Facebook and others. Last year, MySpace cut about 720 jobs, reducing its work force by about 40 percent.