Free Lossless Audio Codec. Unlike MP3s, which discard audio data to shrink file sizes, FLAC compresses audio without losing a single bit of information. It provides bit-perfect replication of the original source material.

included the original album plus a second CD of rarities, demos, and live recordings. Special Collectors Edition

For casual listening on wireless earbuds or phone speakers, a standard streaming file or a 16-bit/44.1 kHz CD rip is perfectly adequate. But Kid A was engineered by Nigel Godrich to be an immersive, psychoacoustic experience. It demands high-end hardware and high-resolution files.