Quadraphonics

This page is devoted to the various "quad" systems that were developed in the 1970s.  Consumer quadraphonic recordings were released on three primary formats - vinyl records, 8-track tapes, and reel-to-reel tapes.  There was also some attempt to develop quadraphonic fm broadcasts, and some audio equipment companies released receivers and tuners that were "quad-ready", but quadraphonic radio never really happened.

Here is a page with tons of information on quadraphonic systems.