In the weeks and months leading up to Microsoft's Zune launch last November, many industry insiders wondered aloud if the Seattle software giant would have its thunder stolen by its neighbor, digital retailing giant Amazon.com, which was also planning to battle Apple's iPod-iTunes juggernaut.

Nearly a year and loads of speculation later, Amazon finally unveiled a beta version of its digital music service, called Amazon MP3.

The new store boasts a catalog of more than 2 million songs from 180,000 artists and 20,000 labels. The music will be sold DRM-free, meaning that downloads won't contain technology that will restrict their use or ability to play on any MP3 player, including the iPod.

Amazon MP3 is almost entirely Web-based, and as such it requires no desktop application to access the service, although customers can choose to use an application that will save downloaded files in either iTunes or Windows Media Player.

Amazon MP3 will seek to capitalize on its already massive customer base, and people with existing Amazon accounts can simply pay for each track from their credit cards already stored with the system. Users can also add digital tracks or albums to a cart that contains other products sold on Amazon.com.

The new service also addresses one of the biggest sticking points between the major music labels and Apple: variable pricing, or the ability to charge different amounts for songs based on demand and popularity.

Half of the 2 million tracks available cost 99 cents, while the other half sell for 89 cents. Albums are also sold under variable pricing, ranging from $5 and under to $9, an indication that Amazon is hoping to sell more digital albums than has been the industry norm to date.

EMI Music and Universal Music Group are the only two major labels participating in Amazon MP3 so far, along with a number of independent labels.

Amazon will likely rely heavily on cross-selling, which involves placing links to the download service on the pages of albums that are available digitally.

Amazon has not said how long the service will be in beta mode.