An optical organ of the type which shines light through the tracks of a rotating optical record onto photocell apparatus and which utilizes depressable keys to play selected tracks, wherein only one or a few photocells are required. The keys are connected to slideable rods that deflect small light control members positioned between the record and photocell. In one organ, the deflectable members are pivotally mounted shutters with corrugated side walls that interfit one another to prevent the leakage of light between the shutters. In another organ, the deflectable members are resilient light-conducting fingers formed in a sheet-like edge portion of a transparent member, each finger being deflectable to a position where its end can pick up light from a particular optical track and carry it to the photocell.
A musical instrument is disclosed in which light beams striking a detector produce various tones and the loudness of the sounds produced is dependent upon the intensity of the light beam which can be changed by interrupting the beam or reflecting the light backwards to a detector situated next to the light source. A special amplifier circuit is provided which responds to both the amount of light beam interruption as well as the rapidity of interruption. The invention can be variously embodied in woodwind, string and percussion instruments and can also be used on a stage and controlled by moving dancers or musicians.
