Digital audio compression and playback standard that can reduce a file size to 1/20th (or even less) of its original size to fit 150 songs (requiring 7.5 gigabytes or more of storage space) on a single CD with very little loss in sound quality. MP3 files can be played back on a computer, or on electronic players with no moving parts. Developed under the sponsorship of Motion Pictures Experts Group, MP3 is by far the most popular software of its kind and is downloadable free from numerous websites.