| 摘要 |
PURPOSE:To obtain the detection output of required relation correspondingly to keying operation by constituting a reflection face so that a distance between a photodetecting means and the reflection face is changed in accordance with the keying operation. CONSTITUTION:When a key 1 is depressed, a projection 2 is moved in the downward direction of the photodetector 4, the distance R between the photodetector 4 and the reflection face 5 is changed and thereby the output of the photodetector 4 is changed. The position and keying speed of the key 1 at the time of depressing it are calculated based on the output change and used as control signals for various musical tone parameters. When the shape of the reflection face 5 is properly selected, the output characteristics of the photodetector 4 can be fixed over the whole keying stroke area. Thus, wide musical tone control can be attained by using the whole keying stroke area. |
