After its first full year selling tracks from all four major labels, Amazon's digital music store has become the second-largest a la carte service, according to industry estimates.

But it's a very distant second to iTunes. Major-label sources say that they had hoped the company would have fared better than it did. Amazon has yet to release any sales figures for digital music, and it did not respond to interview requests for this story. But Piper Jaffray financial analyst Gene Munster estimates that Amazon will sell 130 million tracks this year - a paltry sum compared with the 2.4 billion songs iTunes is expected to sell this year.

Those figures are skewed by the fact that iTunes operates in more than 20 countries, while Amazon just opened its first foreign store onDecember 3 in the UK. But analyst estimates put Amazon's digital-music market share at about eight per cent, atop the "everybody else" category of services competing with iTunes. And that figure didn't go up as the year went on.

"The market share has remained relatively stable throughout the year," NPD Group analyst Russ Crupnick said. "I didn't see anything out there that would be a major game-changer. I'm not all that surprised."

Amazon took on major challenges. Entering a market dominated by an entrenched competitor isn't easy, and the company lacks a branded device to drive sales. Apple drives iTunes sales with its iPod, as the spike in downloads seen after the holidays suggests. And outside of a brief TV campaign supporting its Pepsi Stuff, which let consumers collect points redeemable for MP3s and other purchases, Amazon didn't do much marketing.

Amazon does have a few achievements to crow about, however. Its proportion of digital album to digital single sales is twice that of iTunes, according to the NPD Group. But its album sales are boosted by its weekly discounts, which offer catalogue products for as little as 99 cents.