has launched a public beta trial of its much-anticipated music download service.

Amazon MP3 claims to offer: "The world's biggest selection of a la carte DRM-free MP3 music downloads."

The service offers over two million songs from 180,000 artists and over 20,000 major and independent labels.

Because the music is sold in DRM-free MP3 format, songs purchased from Amazon MP3 will play on iPods, PCs, Macs and other portable and desktop platforms.

Bill Carr, vice president for digital music said: “This new digital music service has already been through an extensive private beta, and today we’re excited to offer it to our customers as a fully functional public beta. We look forward to receiving feedback from our customers and using their input to refine the service.”

A readiness to adopt flexible pricing has clearly helped Amazon reach its distribution deals. Most songs cost between 89 cents to 99 cents per track. The top 100 best-selling songs are 89 cents, unless marked otherwise. Most albums are priced from $5.99 to $9.99. The top 100 best-selling albums are $8.99 or less, unless marked otherwise.

Bitrate is better than iTunes. Each song is encoded at 256 kilobits. Songs are purchased using Amazon 1-Click and are automatically added to their iTunes or Windows Media Player libraries.