The new service boasts over two million songs from more than 180,000 artists represented by over 20,000 major and independent labels.
AmazonMP3 complements the online retailer's existing selection of over one million CDs to offer customers a bigger selection of physical and digital music than any other retailer.
"AmazonMP3 is an all-MP3, DRM-free catalogue of à la carte music from major and independent labels, playable on any device, in high-quality audio, at low prices," said Bill Carr, vice president for digital music at Amazon.
"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."
Every song and album is available exclusively in the MP3 format, encoded at 256Kbps and without DRM software.
This means that Amazon MP3 customers are free to enjoy their music downloads using any hardware device, organise their music using any music management application and burn songs to CD.
Most songs are priced from 89c to 99c, with more than half the songs priced at 89c. The top 100 best-selling songs are 89c, 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.
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