Patent GB-507478-A (GB)
Title: Improvements in electrical musical instruments
IPC: G10H3/22
Filed: 1937-11-11
Abstract: 507,478. Electrical musical instruments. FROHMAN, P. H., and TAYLOR, R. L. Nov. 11, 1937, No. 30963. Convention date, Nov. 20, 1936. [Class 88 (ii)] A tone generator for an electrical musical instrument comprises a free magnetized reed with a pick-up coil adjacent thereto, and means opposite the tip of the reed to modify the voltage curve of the current produced, by the addition ofa harmonic. The output from the reed pick-ups may be variably combined with the output of microphones picking up the air vibrations produced by the reeds, and so modified as to produce flute, diapason, string, and reed tones. In Fig. 1, a coil 16, adjustably mounted adjacent the magnetized reed 13 mounted on the wind or suction chest 10, generates a current corresponding to the normal diapason vibrations which the reed is voiced to give per se, as distinct from reed-quality vibrations added by the edges as they cut the surrounding air. Opposite the tip of the reed is the end 20 of the polepiece 18 of another coil 19. The polepiece 18 alone modifies the harmonics of the current in coil 16, since the magnetic flux is affected each time the tip of the reed passes the end 20. In addition, the octave current induced in coil 19 maybe added to that in coil 16. Further modifications of the harmonics may be produced by varying the position of the pole end 20. Adjustable plates 24 vary the area of the wind-chest aperture, and covered holes 22 break up vibrations in the air column. In Fig. 3, coil 16 is omitted, a permanent magnet 27 in magnetic contact with the reed increasing the. magnetization of the reed. An adjustable screw 21<1> is the polepiece of coil 19 in which is induced the fundamental frequency. In Fig. 4 (not shown), the coil 19 of Fig. 1 is omitted, the polepiece 20 being replaced by an adjustable soft iron bar. A similar soft'iron bar is held in Fig. 5 (not shown) by the core of a,coil 19. In the circuit diagram. Fig. 6, the coils 16 and the coils 19 of a number of notes are respectively connected in series, with resistance controls 36, 38 on the console, and a common return wire 40. The currents from coils 16 and coils 19 in the required proportions are taken by leads 41, 43 to an amplifier 42 with a tone-control 43a, 44 on the console. The amplifier 42 feeds three loud-speakers 48, 49, 50 arranged in parallel and responsive to different ranges of frequencies (strings and upper harmonics, diapason, and flute). Each of these loudspeakers has loudness controls (52, 58, 60) with a swell pedal master-control 54. The reed generators are under a. soundproof cover 25 in the wall of which are arranged two microphones 62, 63 with differing frequency responses to pick up air-waves characteristic of reed-tones and whose outputs are mixed at 66 and taken to an amplifier 68 with a tonecontrol 71, 72 varying the reediness. Amplifier 68 feeds a loud-speaker 74 responsive to reedtones, with loudness resistances 76 and mastercontrol 78. The effect of a mixture stop may be added to the loud-speakers 48, 49, 50 by imposing high frequencies, derived from amplifier 68 by resistance 81 and induction coil 82, on the leads 41, 43 of amplifier 42, by means of brass plates 86, 87 adjacent the core 85 of the induction coil 82.