GB601671A - Improvements in or relating to electrical musical instruments - Google Patents

Abstract

601,671. Electrical musical instruments. MIDDLE DITCH, R. H. P., and HARRISON & HARRISON, Ltd. Dec. 5, 1944, No. 24245. [Class 88 (ii)] In an electrical musical instrument, reeds, vibrated continuously by an air supply, induce electric currents in adjacent electro-magnetic pick-ups and the currents are selectively used to produce the desired sounds. Reeds 1, Fig. 6, of steel or of brass carrying iron armatures, are tuned to cover the range of the instrument and vibrated by wind pressure so as to induce currents in windings around permanent magnets 3 located adjacent to the reed so as to pick up the fundamental and desired harmonic combinations. The outputs are fed through multiple key operated contacts 6, Fig. 1, and bus-bars to potential dividing resistances 7 which determine the amplitude of any desired harmonics. From the potentiometer 7 the currents pass through resistances 16, whose purpose is to prevent a direct connection between any two connected potentiometer tappings. The combined outputs, each comprising selected combinations of harmonics, are passed to a separate control unit 9 for each stop. These units consist of a transformer which, when its stop is drawn, has its primary circuit completed by a switch 11 and a short-circuit removed from its secondary by a switch 10, so that it is connected in series with the secondaries of all other operative stops. Each pick-up device on each reed is connected with the corresponding pick-ups on other reeds to a circuit as described and the final outputs are selectively connected in parallel to the output amplifier. The keys may operate the contacts 6 directly or through relays and in the latter case any desired keys may be coupled electrically. The attack may be varied by causing a resistance to be inserted in the key circuit during the early part only of the key stroke, and an additional set of reeds may be selectively vibrated as in a harmonium. A tone filter may be incorporated to minimize key clicks, the output of the generators being adjusted to overcome attenuation of the higher frequencies.