LOS ANGELES -- Mobile campaigns with custom audio additions have become popular recently, with brands such as BET, MTV, Univision, Fox News, Jamster, Chevy, Sears and CBS dabbling in this fairly new medium.

MTV, for example, has brought live audio to mobile phones, initially with a Daddy Yankee concert, an audience of mobile marketers was told Nov. 14 at the Mobile Marketing Forum in Los Angeles.

"This worked out well because users don't pay for the airtime, as it's included in their plan," said Richard Siber, founder and president of Siber Consulting, at the Mobile Marketing Association-organized event. "All they end up paying for is the actual download."

The Daddy Yankee concert brought in 10,000 callers requesting access to the audio download in just three days. Seventy-six percent requested a call back with information on other events like the live audio.

Once users got the audio download they were then offered deals on Daddy Yankee ringtones. MTV sold 1,300.

Mr. Siber also talked about Mobile Idol, "which brings social networking from the Web to the mobile phone."

Users record themselves singing a song into the receiver of their mobile phone, with the actual melody playing in the background. They are then given the option of posting the recording onto a Web site where other users can rate how good it is. The rater can choose to purchase the audio and use it as his or her ringtone.

"Making audio available on phones gives marketers just another way to monetize," Mr. Siber said.