history and function
http://en.wikipedia.org/wiki/Stereo_8
difference in sound
the 8 track sounds different compared to other formats. the 8 tracks' 1/4 inch tape is wider, thicker, and moves twice as fast as cassette. this means that more information about the sound/music is recorded to tape per-second. this gives a purer tone to the recording. because 8 track is analog, it is generally warmer and more natural sounding than cd/mp3/digital, which is relatively harsh, lacks the presence tape has, and filters out any holographic effect. if production of an 8 track is all done in the analog domain the holographic effect is preserved to varying degrees. compared to vinyl, 8 track has more punch, is less brittle sounding, and once again, records more of the holographic effect due to being magnetically analog (tape) vs. physically analog (grooves/bumps). the only format that trumps the 8 track is the higher speed open reel-to-reel tape. however, reel-to-reel has it's limitations (cost, availability, weight, skill of use) that makes 8 track the best compromise in listening.