Patent GB-403204-A (GB)
Title: Improvements in or relating to electrical musical instruments
IPC: G10H5/10
Filed: 1932-10-07
Abstract: 403,204. Electrical musical instruments; condensers. HALMAGYI, J., and LANGER, N., 10, Veres-PalnÚ-utca, Budapest, Hungary. Oct. 7, 1932, No. 27973. [Class 88 (ii).] In an electrical musical instrument employing a glow discharge lamp G, Fig. 1, in series with a condenser C1 and source of current B, the oscillations being transmitted by a transformer T to a loudspeaker L or utilised for broadcasting, one or more of a multiplicity of resistances R1-Rn arranged in series are connected across the condenser C1 by the keys K1-Kn (switches d3 and S2 being closed) so as to produce the notes of the scale successively from the one lamp. Polyphonic music is obtained by the use of a number of such circuits, if desired with common battery and output transformer. Or by keeping a key closed and rapidly and repeatedly closing a higher key, the impression of two simultaneous notes may be obtained. Volume is controlled by potentiometer P2 across the secondary of the transformer T ; general tuning or transposition by potentiometer P 1 across part of the current source (or by variation of condenser C1) ; timbre by connecting, by a switch S4, capacities C3, resistances, or inductances L1 across the primary of transformer T. A discontinuous tremolo may be obtained, with switch d3 still closed, by making and breaking contact d1, throwing in and out a small condenser C2 in parallel with condenser C1. A banjo or mandolin effect is obtained by closing switch d4 in lieu of d3, and rapidly moving lever A to and fro on contacts d1, d2. The lever A may be constructed to rock in two directions at right angles so as to operate both the switches d1, d2 and also the volume control P2 (Figs. 6, 7 not shown). For individual tuning, instead of varying the resistances R1-Rn, each key K1-Kn may be connected to one of a number of potentiometers in parallel across a second current source (Fig. 2 not shown). A smooth tremolo may be obtained by the use of a variable condenser (Fig. 3 not shown) comprising a curved plate of spring brass which can be flexed by the finger towards a plane brass plate, a sheet of mica intervening. Fig. 4 shows a second circuit II, similar to the main circuit I but having a large condenser C2 and high resistance R2, for producing low frequency tremolo oscillations which are automatically imposed on circuit I containing the loudspeaker. Another arrangement (Fig. 5, not shown), in which a high capacity condenser is connected across the current source, produces a modified banjo effect in which the pitch of a note falls and rises as contacts are broken and made by hand. To imitate the fading away of piano tone, a note-key KN, Fig. 9, also makes a passing contact at d7 charging a condenser CX (adjustable by means of condensers CY, CZ) which quickly discharges, varying the plate voltage, and therefore the amplification factor, of amplifier N. A number of different timbres may be simultaneously obtained from one lamp, by providing transformer T with a number of secondaries each with a separate tone-control switch connecting different capacities, inductances, and /or resistances across the circuits to suppress or to stress the higher harmonics. These circuits may, if desired, be recombined by a transformer with one secondary (Fig. 10, not shown). The glow discharge lamp may be covered by an opaque shield, preferably of metal. The main circuit through the lamp should preferably remain closed even when the instrument is out of use. To avoid risk of reaction from the amplifier to the oscillator and to eliminate contact noises, a photo-electric cell or cells Ph, Fig. 8, may be used, influenced solely by the light periodically emitted by the glow-discharge lamp or lamps G. Filters or diaphragms D may be arranged between the lamp and the cell to control volume or timbre. Specifications 353,918 and 390,678 are referred to.