GB401537A - Improvements in or relating to electrical musical instruments - Google Patents

Abstract

401,537. Electrical musical instruments ; transmitters. PALMGREN, N. A., 8, Gibraltargatan, Gothenburg, Sweden. Feb. 7, 1933, Nos. 3767 and 3768. Convention dates, Feb. 8, 1932 and July 28, 1932. [Class 88 (ii).] In musical instruments wherein the vibrations of mechanically or electrically vibrated members such as electrically conductive strings, springs &c. are electrostatically translated for transmission to a loud-speaker, recording-apparatus, or the like, the size or disposition of an electrode relative to the vibratory members differs between the members. In Fig. 4, the strings 1, sounded from keys 11 by hammers 12, are connected to a battery 7, transformer 8 and electrode or electrodes 2a, 2b forming condensers with the strings, the secondary of the transformer being connected through a potentiometer 9 (with pedal-controlled movable contact) to the loudspeaker &c. Different timbres are produced by the electrodes 2a, 2b, either being connected in circuit by a switch. A tone richer in harmonics is obtained from an electrode covering a portion only, as compared with the whole, of the length of a string. The timbres of different strings, or the characteristics of the amplifier or loudspeaker, may be adjusted or corrected by varying the size and disposition of an electrode relative to the strings. The electrodes consist of vibration - deadening material with a facing of sheet metal, wire netting, or metal powder in a suitable binder ; or they may consist of tuned vibratory members. In Fig. 7 metal bands 1 lie between two perforated electrodes 16, 17 and are connected in such a way that in depressing a key 30, which co-acts with three contacts 23, 22, 21, first the potential of the band 1 is changed, thus setting it in vibration, and then the vibrations are transmitted to the loudspeaker 29 as before. An electrode may be screened from disturbing electrostatic effects on the side remote from the strings by an extension of the string-frame, on which extension the electrode may be adjustably mounted (Figs. 8 to 10 not shown).