GB1418516A - Key system for electronic musical instruments - Google Patents

Abstract

1418516 Electrophonic musical instrument A MICHEL 15 March 1973 [17 March 1972 3 Oct 1972] 12418/73 Heading G5J To control the individual build up of e.g. 1800 notes of the register of an electronic instrument, activated typically by 60 keys, each key 11 on closure produces in its circuit A a rising voltage U s (Fig. 2) across load 16, the rate depending on supply voltage U A and on the R-C circuit 10, 13, 14. Each register note is supplied with appropriate sound signal superimposed on direct voltage U t , this signal being passed fully to the common output line above resistor 20 via transistor 19 in circuit B, individual to the register note, when the input current i to the transistor base exceeds i z . The build-up to this condition depends on the instantaneous voltage U s and on the resistor 17 individual to the register note; resistor 17a is added if voltage rather than current control is required. Key switches 12 may be replaced by key position-sensing devices such as photo-electric, saturable-core reactor or air-dielectric capacitor types (Figs. 3, 4, 5, not shown). The signals to circuits B may be taken direct from these devices, giving build-up dependent only on key displacement, or such a device in place of switch 12 in circuit A may initially provide position-dependent voltage U s , superseded by a rising time-dependent voltage when the latter is the larger (Fig. 7, not shown). Resistor 17 again controls the current taken by an individual note circuit B. To improve resemblance to sounding of an organ pipe, a direct voltage source U v individual to each register note is introduced in series in the ground line (Fig. 6 not shown) between resistors 16 and 20 to distort the audio signal to an extent depending on the value of V v and on the progress of the build-up.