Variable filter circuit, especially for synthesizing and shaping tone signals
AssigneeKimball International, Inc.
InventorsBilly J. Whittington, John William Robinson, Ralph N. Dietrich
Life of this patent
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Abstract
A variable filter circuit, especially for synthesizing and shaping tone signals, in which a variable light source is provided which influences light sensitive resistor elements in the filter circuit. The variable circuit, by the use of selector switches, can provide different musical features, such as muted voices, percussion, brass, woodwind and the like, all of which will enhance, for example, existing organ voicing while it is, furthermore, possible to obtain the effect of playing a solo instrument together with organ voicing.
Claims20
The method of producing special sound effects in an electronic organ having a tone generator, an output circuit including an acoustic transducer, and playing keys with each key when depressed controlling the supply of a respective tone signal from the generator to the output circuit, said method comprising:
- interposing a filter circuit comprising a first amplifier, a second amplifier and a third amplifier connected in series in the order named and connected between the tone generator and output circuit,
- interposing a variable impedance element in the inputs to each of the second and third amplifiers,
- said filter circuit having a high pass filter characteristic output, a band pass filter characteristic output and a low pass filter characteristic output corresponding to respective ones of the first, second and third amplifiers,
- detecting the depression of a key and generating a transient control signal,
- controlling the rise and the decay of the transient control signal, and
- varying the values of the variable impedance elements in accordance with the transient control signal to vary the characteristics of the filter circuit.
An electronic organ having a tone generator and a transducer and a keyboard having playing keys with each key when depressed controlling the supply of a respective tone signal from said generator to said transducer means, a circuit interposed between said tone generator and said transducer and operable for modifying the wave form of signals passing from the generator to the transducer means, said circuit having a signal input terminal and at least first and second signal output terminals, a variable impedance means operatively connected in circuit with each of said first and second signal output terminals to modify the wave form of the signals supplied to said first and second terminals, first means operable in response to the depression of a said key for generating a transient first voltage signal, second means manually operable for developing an adjustable second voltage signal, voltage sensitive means operable when actuated to cause variations of said impedance means, and selector means operable for connecting said voltage sensitive means for being actuated in response to a selected one of said first and second voltage signals.
Dependencies are inferred from the claim text.