Surround Sound, BEFORE Dolby

In the 70's, well before all this Dolby Digital 5.1 surround sound or even it's predecessor, Dolby Surround that came out in the late 80's and 90's, we had stereo.  And it was good.  Quadraphonic was an interesting experiment for the 70's, but required re-buying all the stereo components to be Quad compatible.

Some devised a solution; a very crude yet strangely effective solution and it looked like this:

 There is the single zip cord on the bottom of the diagram, tied to the positive speaker posts.
This is how we made surround, with a single speaker in the back of the room. 

Many amps/receivers had two pairs of speaker outputs (for what I am describing, they needed to be isolated from each other) and a switch often labeled "A", "B", and "A+B" to play two pairs of speakers at once.  Maybe one pair was in the living room and the other pair on the porch.

In this case, the "B" pair is the surround speaker.  You turn the speaker selector to "A+B" and you get....surround sound from ANY stereo source.  Any sound not common (in perfect mono and in phase) to the left and right channels plays out the surround  (sometimes FM noise and tape-head azimuth problems resulting in phase errors on the stereo program).  But for a quick-and-dirty means, this was great.  Often the vocal track would disappear here (unless mixed in mid-60's "Beatles-type stereo)
leaving the rest of the music on it's own.  Nothing was MIXED for surround.  It just worked in various ways on various soundtracks.  And it was COOL.  A view to the future, when Quadrophonic was reborn in a sense as......5.1 Surround sound!