GB1203162A - Electronic musical instrument - Google Patents

Abstract

1,203,162. Electrophonic musical instruments. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 12 Sept., 1968 [15 Sept., 1967], No. 43403/68. Heading G5J. In a keyed electronic musical instrument comprising a plurality of tone generators each coupled to an output via an individual gate, each key being adapted to charge a capacitance to a voltage which increases with the strength of actuation of the key, and the capacitance voltage being fed to an actuating terminal of a gate for unblocking the gate to an extent which increases with the magnitude of the voltage, the difficulty arises that if the discharge time of each capacitance is short the tone decays too rapidly whilst if it is long the note cannot be repeated soon after a strong actuation. This is avoided by making the capacitance discharge rapidly at first and more slowly thereafter. In Fig. 2a the capacitance comprises two capacitors C1 and C2 in series each charged through a respective diode by voltage induced in associated coils S1 and S2 when the key moves the magnets M1 and M2. The initial discharge is mainly of C2 through R2 and takes 0À1-0À2 seconds; the next stage of the discharge is of C1 through D3 and R1 and has a time constant of two to four times the initial value; finally when the diode D3 cuts off, the discharge is through the load R and has an even longer time constant. In a modification (Fig. 3, not shown) the components S2, D2, C2 and R2 are omitted, and in another modification (Fig. 4a, not shown) the capacitor C2 is omitted; in this latter case the resistance (R S ) in series with D2 should have a value of about five times the critical damping resistance of the circuit comprising the coils, the capacitor and the resistance.