Matrix quadraphony is a technique for “matrixing” or combining several original program channels having presssigned angular positions into two audio-frequency channels (e.g., of a stereophonic disk record) for reproduction over four loudspeakers which surround the listener. Practical utility and realistic spatial reproduction of the original channels requires the use of a matrix code and a position-responsive time-sharing mechanism capable of (a) full compatibility with existing stereophonic and monophonic sound reproduction media and devices, (b) providing adequate positional cues, codable into the matrixed channels and recoverable therefrom, and (c) complementary cooperation with the psychoacoustics of human hearing. A description of a quadraphonic disk system (The SQ™ Disc Record System) responding to the above requirements is given.