PURPOSE: To make it possible to reproduce clearly either one of sound information signals, sum signal and difference signal, by generating those two signals by a matrix circuit and then by recording both the signals on two tracks separately.

CONSTITUTION: To input terminals 9 and 10, a main signal and sub signal bearing no mutual relation are inputted respectively. In case of TV sound multiplex broadcase, duplex sound broadcast can be discriminated by a control signal frequency. Those main and sub signals are supplied to matrix circuit 11, where a sum signal and difference signal are generated and outputted from output terminals 12 and 13. The sum signal outputted from terminal 12 recorded on a 1st sound track by audio head 14, and the difference signal from terminal 13 on a 2nd sound track by audio head 15. To reproduce the both by a unit with only one audio head, mixing both the signals redults in (main signal + sub signal) + (main signal - sub signal) = 2 × (main signal), so that only the main signal will be outputted.