Microsoft Corp co-founder Bill Gates' privately held Corbis, which provides photos and film video for advertisers, is expanding further into entertainment by launching an online music service with songs from the four largest publishers.

The GreenLight Music service went live on Wednesday, with more than 1 million tracks from catalogs controlled by Warner Music, EMI Music Publishing, Universal Music and Sony ATV.

Corbis , which the Microsoft chairman started in 1989 by securing the digital rights to such art masterpieces as the "Mona Lisa" and "Whistler's Mother", created GreenLight in 2008 and used it to jumpstart efforts to transform itself .

Its new music service will let customers license a range of songs for online websites, advertising and other professional uses. Users bid on the tracks, with the labels negotiating the final price.

Under Corbis CEO Gary Shenk, the company has been steadily buying and starting entertainment services. In January, it acquired Norm Marshall & Associates, which brokers deals to place clients' products in movies and on TV shows.

In February, it launched On Demand Entertainment, a subscription service which allows users to license celebrity photos and other entertainment images.

"Our customers want to connect to entertainment to break through the clutter so we decided to give them access to iconic entertainment," said Shenk. In one case, he said, Corbis provided video clips for Hasbro Inc to include in its online version of Trivial Pursuit.

The use of the Monkees ' song "Daydream Believer" was recently licensed for $1,875 for a corporate meeting, the company said.

"It's our responsibility to find new and innovative ways to help EMI's artists achieve the success they always dreamed of," Brian Monaco, EMI's executive vice-president of sales and strategic management, said in a statement. "And we're committed to finding ways to simply the sync licensing process."

Green L ight marks Corbis' tentative foray into the market for online music sales. But Shenk said the company has no plans at the moment to create a service for consumers similar to Apple Inc 's iTunes or Google Inc's music service. (Reporting By Ronald Grover; Editing by Richard Chang)