| 摘要 |
PROBLEM TO BE SOLVED: To instruct a sound source for the tempo of a musical sound to be automatically played without using an expensive band pass filter. SOLUTION: An LED 1 emits an optical beam during the drive signal from a pulse generating circuit 5 is ON. A PD 2 receives the optical beam reflected by the hand of a conductor and external light to generate a light receipt signal. A CPU 4 generates a first detection signal by the light receipt signal including the optical beam from the PD 2 while the drive signal is ON, and generates a second detection signal by the light receipt signal including only the external light from the PD 2 while the drive signal is OFF. When the amplitude difference between the first and second detection signals exceeds a prescribed threshold, a light shielding is detected, and the tempo of the musical sound is temporarily set on the basis of the time interval of the second light shielding. When the tempo is judged to be musically proper as the tempo of the musical sound to be automatically played of the music of a music data ROM 12, the playing control of the musical sound to a sound source 13 is performed with this tempo. |
