PURPOSE: To simplify the circuit constitution by providing an object emphasis characteristic to each of input circuits of an FM modulation circuit comprising an oscillation circuit whose oscillating frequency is varied depending on the current generated from a current source and the plural input circuits varying the current generated from the current source in response to the signal.

CONSTITUTION: A signal VA is impressed to an input terminal 30A and zero or a negative voltage is impressed to an input terminal 30B to turn off a transistor (TR) 6. The signal VA is converted into a current by a TR 5 and in this case the signal is subjected to emphasis processing by resistors R3, R4 and a capacitor C2. Since the change in the collector current of the TR 5 is a change in the current flowing through TRs 3, 4, the oscillating frequency of the multivibrator is demodulated while being subjected to emphasis processing. Thus, the output signal V0 subjected to emphasis processing and FM modulation suitable for the recording system A is obtained. Conversely, in applying the signal processing suitable for the recording system B, the TR 5 is turned off and a signal VB is impressed on the input terminal 30B.