Musical instrument circuit providing celeste and vibrato effects

#Many pipe organs employ one or more ranks of pipes which are purposely detuned from the balance of the organ to produce an effect called "celeste". This effect is a warm, broad, and undulating sound having random beats generally of one to six beats per second (depending on what portion of the keyboard it is played) when this "celeste" rank is played in conjunction with a rank of pipes having similar tone quality and volume. In the electronic organ field, attempts to achieve this effect have been tried using slowly rotating speakers, slowly moving baffles in front of speakers, and/or slow phase modulation.

#For many reasons, these attempts have fallen short of the desired effect but the obvious solution of providing a separate additional rank of electronic generators to provide this effect has been resisted by electronic organ manufacturers because of its relatively high added cost (as compared with a pipe organ) of adding so much circuitry for the achievement of this effect.

#Novel and unique means are herein defined where this effect is achieved at very low added cost in an organ that has rank or a set of 61 notes, for example, of keyed oscillators of special design together with at least one other rank or set of tone generators. This rank of oscillators, when keyed at the normal voltage provides a unit stop of some useful character such as "principal" or "gemshorn" or "string" for example, but when keyed at the lower "celeste" voltage is detuned such that when combined with the other rank of tone generators at unison pitch, the desired "celeste" effect is produced.

#The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings in which;

#FIG. 1 is a circuit diagram showing one embodiment of the invention;

#FIG. 2 is an alternate keying circuit diagram for use with the circuit shown in FIG. 1;

#Referring to FIG. 1, an oscillator is shown consisting of transistor 12, tapped inductor 7, capacitor 8, and bias network for transistor 12 consisting of resistors 9 and 10. The base of transistor 12 is connected to one end of inductor 7 through resistor 10 and the emitter of transistor 12 is connected to the top of inductor 7 through resistor 11.

#Keying voltage is applied to this oscillator through resistors 13 and 15 and capacitor 14 so that the attack and release may be controlled and may be adjusted to a pipe-like quality.

#When the oscillator is keyed into operation by action of key switch 20, a sine wave appears across inductor 7 and capacitor 8. This sine wave supplies A.C. current to point 6 through capacitor 3. Point 6 is supplied with D.C. current through resistor 4 from the emitter of transistor 23. These two currents add in point 6 and as long as the sum is positive, diode 5 is in conduction, and point 6 is effectively connected to ground through diode 5. When the sum of these two currents is negative, diode 5 goes out of conduction and the voltage at point 6 goes below ground potential. The amplitude of this sine wave across inductor 7 is dependent on the amount of keying voltage actually reaching point 16 and several means are shown for controlling this voltage. The higher voltage across inductor 7 (normal keying voltage) causes diode 5 to go out of conduction for a larger portion of the cycle as compared with when the lower voltage appears across inductor 7 because this higher voltage causes increased current to flow through capacitor 3 into point 6, which in the negative portion of its cycle, cancels the D.C. current supplied by resistor 4 into this point for a larger portion of the cycle.