Does Amazon's plan to sell music downloads provide some added momentum to the music industry's transition to the sale of restriction-free music downloads? Yes.

Will it provide some badly needed competition in a market dominated by Apple's iTunes Store? Yes.

But will Amazon , the undisputed champ of online retailing, swoop in and save the day for downtrodden record companies? Not a chance, at least not based on what we know so far.

Digital music sales currently account for about 10% of overall worldwide music sales. To get significantly beyond that level, the music industry not only needs to increase the number of major online vendors selling downloadable music but also needs retail partners whose interests are more in sync with its own than Apple.

Apple is in the business of selling high-margin iPods. Music is a sideline. Nonetheless, the company accounted for 70% of song download sales in the U.S. in 2006, according to market-research firm NPD Group. Reducing Apple's market dominance is one of the key challenges facing the music industry as it works to further increase digital music sales.

Record companies are enjoying strong digital sales growth, but the gains still don't come anywhere close to making up for the continued erosion in CD sales. It's also far from clear how much digital music sales will benefit from the dropping of usage restrictions. Most people don't even know they're being restricted. And many of those that do are still trolling online for free music. They don't seem all that interested in low-cost or rights-free music, regardless of format. They want free music. Period.

Amazon provided little information about its plans, including exactly when it will start selling downloads, how much they will cost or how it will integrate the downloads into its Web site. But the key detail was this: The company will sell music from EMI Group and independent record labels as restriction-free MP3 files, a universally compatible format that can be played on any handheld music player, including Apple's market-leading iPod. They are also compatible with any cell phone equipped to play music.

Due to concerns about piracy, the four major record companies--Universal Music Group, Sony BMG Music Entertainment, Warner Music Group and EMI--have long sold virtually all of their song downloads with usage restrictions, also known as digital rights management, or DRM.

But EMI, which has been particularly hard-hit by the industrywide decline in the sale of compact discs, broke ranks in April when it announced that it would begin selling its music on iTunes without restrictions and that it was willing to do so via any other online music retailer as well.

Amazon is the first major retailer since Apple to take EMI up on its offer. By opting to use the MP3 format, Amazon one-ups Apple, which plans to sell restriction-free songs from EMI in the AAC format, which is compatible with the iPod and a handful of other music players, but can't be played on many others.

But it's hard to imagine a mainstream online music retailer like Amazon selling many song downloads without the participation of the other major record labels. EMI is the smallest of the majors and has a catalog that is shorter on big U.S. hits than its larger counterparts.