In the late 1960s, after the stereo sound almost completely replaced the mono format in the recording industry, the attention of engineers was shifted to quadrophonic sound technology.

Unfortunately, at that time, quad-sound was not widespread due to equipment manufacturers failing to develop a common quad standard, releasing recordings and record players of various formats to the mass market which made it hard to find a match.

Nevertheless, quad recordings forced the sound producers to make special mixes which differed from the stereo mixes not only in sound design but also by the inclusion of other takes. This created a particular niche for collectors and die-hard fans who hunted the rare quad vinyl releases to experience the well-known recordings with the fresh colors.

In the early 1970s, first quadraphonic LPs came out with three incompatible systems: SQ by CBS Records, CD-4 by RCA and QS by Sansui. New records were released only for one of these standards and consumers could not listen to quadrophonic sound if they had a different system.

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