Too Long; Didn't Read
Advent of Computing: extreme lo-fi edition. How I Compressed Each Podcast Episode to Less Than a Floppy Disk's 1.44 MB Limit. The trick to all of this is encoding. MP3 is the most familiar, but you also have formats with better compression like AAC, or lossless formats like FLAC and WAV. AMR is an audio coded that's widely used for transmitting telephone calls over GSM networks, but it can just as easily be used to encode full audio files.