Website MySpace is to allow unsigned bands featured on the social networking site to sell their music as downloads.
MySpace has grown massively since its launch in 2003
The site - which has 106 million users - is currently testing the idea, and hopes to rival market leader iTunes.
Nearly three million bands feature on the site, with individual bands set to decide on the price of their tracks.
"The goal is to be one of the biggest digital music stores out there," MySpace co-founder Chris DeWolfe told news agency Reuters.
"Everyone we've spoken to definitely wants an alternative to iTunes and the iPod. MySpace could be that alternative."
MySpace, which is owned by media giant News Corporation, currently allows visitors to the site to listen to up to four songs per band - but these cannot be bought.
"A band in Iowa can now reach out to fans in Los Angeles," said Mr DeWolfe.
"They can actually sell their music on MySpace in an area where their fans congregate in a very contextual manner."
In the past year, MySpace.com became the single most visited internet address among US web users - although that position is now strongly contested by video site YouTube.
Music downloads have soared in popularity in recent years, with Europeans alone expected to spend 280m euros (£189m) buying music online this year.
The announcement from MySpace is the latest development in the fast-changing area of music and social networking sites.
In July, Sony BMG struck a partnership with British site Faceparty to have its artists promoted exclusively to the site's six million members.
Last week Vivendi Universal, the world's biggest music group, signed a deal to make its music catalogue available on a free legal downloads service through entertainment site Spiralfrog.
Under the agreement, Spiralfrog will offer Universal's songs online in the US and Canada.
Meanwhile, YouTube has declared its ambition to place every pop video ever made on its site.