GB369838A - Musical instruments, in which music is produced by frequency alterations of electricoscillations - Google Patents

Abstract

369,838. Electrical musical instruments ; electric resistances. LERTES, P., 55, Kuhwaldstrasse, and HELBERGER, B., 37, Zeppelin-Allee, both in Frankfort-on- Main, Germany. July 13, 1931, No. 20079. Convention date, July 16, 1930. [Class 88 (ii).] In a musical instrument operated by electric oscillations generated by a valve 13, the frequency is varied by means of a potentiometer controlling the grid potential of the oscillating valve. The contact element of the potentiometer comprises a metal band fixed to a block 3a and supported at the other end on a trestle 3b, this end being maintained in tension by a spring 5 acting through a block 4 pivoted at 6. The contact band is covered by a slightly wider band 1b of leather or other supple insulating material and is adapted to be depressed by the operator's finger-tip at any desired point on to a resistance element 2a of convex section on its upper face. The block 4 carries an arm 7 engaging a mercury cup 8 whereby depression of the band 1b makes the circuit of the grid battery 16 through the resistance 2a before contact of the band with the resistance is established. The resistance element 2a is supported by a cloth band 2b secured at its free end to a spring-controlled lever 9 on which is mounted the movable primary coil 12 of a transformer coupling the oscillating circuit to an amplifying valve. The resistance 2a is preferably wound as a spiral of varying pitch so that a given shift in the contact point corresponds to the same musical interval throughout the length. In an instrument comprising several voices, the potentiometers are arranged at different levels on sloping supports to facilitate playing.