QUADRAPHONIC RECORDING SYSTEM

Apparatus for recording four separate channels of sound information on the two tracks of a stereophonic disc record for subsequent reproduction on four loudspeakers to give the listener the illusion of sound coming from four separate sources. Two of the four signals are applied to respective ones of the two tracks, as in stereophonic recording, with the third and fourth channels superimposed thereon by applying equal in-phase portions of the third signal to both of the tracks and by applying equal portions of the fourth signal to both of the tracks with a differential phase angle between the two portions which remains substantially constant throughout the audio frequency range of interest. The fourth signal applied in this way causes the stylus of a stereophonic cutter to describe an ellipse having major vertical and horizonal axes disposed normal and parallel, respectively, to the surface of the record.