Spensley, Horn & Lubitz
Electronic musical instrument having an electronic filter with time variant slope
 An electronic musical instrument capable of changing a slope portion of a filter characteristic continuously from start to completion of production of a musical tone. The inventive electronic musical instrument changes a filter slope in a frequency region above or below a cut-off frequency with lapse of time and, in order to achieve such change in the filter slope, changes a slope factor continuously from start to completion of production of the tone. The instrument is also capable of changing the cut-off frequency. An example of a low-pass filter is shown in which a desired form of a successively changing filter slope can be obtained by employing four slope factor values and three values representing a speed of change of the slope factors as well as three cut-off frequency values and two values representing a speed of change of the cut-off frequencies. 
Nippon Gakki Seizo Kabushiki Kaisha
G G
G10H G10H
inventional inventional
Masanobu Tsuyoshi Hideo
Chibana Futamase Yamada