iPod and iTunes: The Missing Manual, Third Edition

Chapter 4. Digital Audio Formats

Recorded music has appeared in a variety of shapes and sizes over the decades, including fragile discs spinning at 78 rpm, vinyl records in colorful sleeves that were artworks in themselves, pocket-size cassette tapes, and futuristic-looking compact discs. But no music format ever exploded into the public consciousness as quickly and widely as the bits of computer code known as MP3 files.

The MP3 format makes it possible to compress a song into a file small enough to be uploaded, downloaded, emailed, and stored on a hard drive. That feat of smallness set off a sonic boom in the late 1990s that continues to reverberate across the music world today.

This chapter tells all about MP3 and other music formats, including the main iPod–approved format: AAC (Advanced Audio Coding), a copy-protected file type that makes Apple’s iTunes Music Store possible.

Introduction to Digital Audio

The era of modern digital audio began in the early 1980s. A new, small, shiny format called the audio compact disc, developed by Sony and Philips, began to appear in music stores alongside albums on tapes and vinyl records. Unlike analog tapes and LPs, audio CDs stored music in digital form, and produced a bright, clean sound with pristine clarity. (Some audiophiles still prefer the “warmer” sound of vinyl, not to mention the expansive canvas that records provided for detailed album artwork, but many have accepted the CD.)

1985 was a pivotal year for the CD. The format’s popularity ...