PURPOSE: To ensure the more accurate judgement by a visual aid for the starting time of a song which is usually indicated acoustically, by lighting up a song starting means at a stereo sound recording part including the monaural and sound recording parts on a tape.

CONSTITUTION: Both L and R channel signals of a tape including a monaural sound recording part M and a stereo sound recording part S are fed to a comparator 2 via a low pass filter 1. The signals of both L and R channels have the same size and same phase at the part M, and accordingly the output of the comparator 2 is zero. While at the part S, an output is produced from the comparator 2 since a phase difference exists between the signals of the channels L and R. Thus the starting time of a song is accurately indicated by the glowing of a light emitting diode via a phase difference level detecting means 3. For instance, the 3rd glowing of the diode 4 indicates the starting time of a song in the case of an introduction part I comprising S, M, S and M. In such way, the more accurate judgement is possible with a visual aid in addition to a conventional acoustic aid for the starting time of a song.