Norlin Industries, Inc.

Norlin Music, Inc.

Glenn M Gross

Douglas R Moore

This is an electronic organ which economically simulates long duration aperiodic musical waveforms, such as the clash of cymbals. It employs the digital waveform generation technique, in which successive instructions are read out of a memory to determine the amplitude of the waveform at successive sample points. To save memory capacity, the memory addresses are rescanned; and to avoid audible discontinuities the scan direction recirculates numerically back and forth across the address field. Despite the bidirectionality of the scan, monotonic decreases in amplitude and in higher harmonic content are achieved. The monotonic decrease in amplitude is accomplished by impressing an exponentially declining envelope upon the digitally generated amplitudes. The monotonic decrease in higher harmonic content is accomplished by preventing the rescan from returning to a memory region of greater harmonic content after it has once entered a region of lesser harmonic content.

Long duration aperiodic musical waveform generator

A tone source apparatus for an electronic musical instrument includes a sequentially addressable memory storing a plurality of waveform segment defining instructions, each instruction including a component representative of the amplitude variation, the time duration and the direction of change of the associated waveform segment. Output means comprising an adder-subtractor circuit and a latch is operated for accumulatively processing the stored amplitude variation representative components for producing a stepped output signal whose direction of slope is determined by the stored direction component. Control means interposed between the memory and the output means is selectively operable for modifying the stored amplitude variation components coupled to the output means for imparting a sinusoidal inflection to the stepped output signal.

Complex waveform generator for musical instrument

A waveform generator for an electronic musical instrument comprises a signal generator (10) developing a binary signal sequentially increasing and decreasing in value at a selected rate and a memory (26) storing a plurality of parameter instructions at respective memory addresses, each memory address corresponding to a continuous group of values of the binary signal. An addressing circuit (24) addresses each memory address in response to the binary signal assuming a value within the group of values corresponding thereto. The binary signal is processed with the addressed parameter instructions in an arithmetic circuit (22,40) for developing a linear piecewise approximation of a desired waveform signal.

Linear piecewise waveform generator for an electronic musical instrument

An envelope is imposed on a sequence of binary waveform samples representing a musical waveform signal by repetitively summing selected ones of a group of scaled representations of each of the waveform samples of the form A/2.sup.m, A/2.sup.m+1 . . . A/2.sup.m+p, where A represents the magnitude of the waveform sample, p is a predetermined integer, and m is an integer changing by a factor of unity each time a predetermined number of the groups have been developed. The sum of each group of scaled representations differs from the sum of the preceding group by the factor A/2.sup.m+p whereby a staircase signal is produced amplitude modulating the musical waveform signal, the step size of the staircase signal charging each time said predetermined number of groups have been developed.

Digital envelope modulator for digital waveform

An electronic musical instrument includes a p-bit memory sequentially storing the resolution contributing bits of a sequence of n-bit samples, the n-bit sequence representing a percussive-type waveform. The p-bit memory is sequentially addressed with each stored sample being suitably scaled for reestablishing the magnitudes of the corresponding n-bit samples, the scaled samples being coupled through a digital to analog converter for producing an output signal representing the percussive waveform and having a uniform signal to quantizing noise ratio.

Digital waveform generator having constant signal to noise ratio

A digital technique for triangular musical waveform generation is disclosed. A musical scale value corresponding to a selected note is repetitively added to produce an ascending series of non-consecutive numbers which is stored in a latch. A carry output from the limited modulus latch is used to switch a flip-flop which then enables an inverter to reverse the slope of the number series. Alternating reversals produce a rising and falling numerical staircase of controllable slope. This can be directly converted into a smooth triangular waveform, or alternatively it can be used as a series of memory addresses for table look-up purposes. The triangular waveform may be symmetrical, or it may have a controlled degree of asymmetry. Duplicate triangular waveforms with a small frequency mismatch may be used to produce a chorus effect. Or plural triangular waveforms with octavely related frequencies may be used as footages related to a single note, again with a slight frequency mismatch for chorus purposes. The frequency mismatch is effected by introducing extra pulses into the ascending number series by means of a synchronized carry input to the latch. When used in the table look-up mode, the invention permits great savings of waveshape memory capacity by the use of half-cycle and quarter-cycle symmetry. The latter feature is achieved by the use of a format translation from binary offset to sign-magnitude notation for table look-up purposes, after which the resulting waveshape is converted back into the original binary offset notation. The table look-up approach is also used in conjunction with plural triangular waveforms, by virtue of time-division multiplexing.

Tone generation system employing triangular waves

A high resolution fractional divider is responsive to a multi-bit divisor representative control word and a clock signal for developing an output signal having an average frequency of the form n-f, wherein n is an integer determined according to the most significant bits of the control word and f is a fraction determined according to the least significant bits of the control word.

High resolution fractional divider

A musical instrument tone generator comprises a clock circuit including means for developing an interval code representing the number of musical intervals to be swept by a tone signal. An output clock signal is produced in response to the interval code for causing the swept tone signal to exhibit a rate of change varying exponentially with time such that a number of musical intervals are swept in a corresponding number of equal time intervals. Means are provided for suitably updating the output clock signal in response to the modification of an on-going frequency sweep in order to maintain the foregoing correspondence between the number of musical intervals swept and the time duration of the sweep. In another embodiment, the output clock signal is effective for operating the tone generator for developing a tone signal sweeping one or more musical intervals in an equal time interval.

Portamento and glide tone generator having multimode clock circuit

In order to tune the frequency characteristics of a filter or oscillator as an exponential function of the position of a note on a musical scale, a pulse stream with an exponentially scaled duty cycle is used to gate an on-off switch which controls an electronic tuning signal for the first or second stage of the filter or oscillator. The pulse stream source can be a pulse code generator responsive to a priority note generator, or it can be an oscillator-driven one-shot with an exponentially scaled power supply governing the charging rate of a reactive component which determines the one-shot cycle time. There are also pitch offset and pitch modulation features in the circuit, the latter being usable in a constant deviation or a constant interval mode.

Programmable current source for filter or oscillator

In an electronic organ of the time-sharing type, a single clock source drives a number of variable divisor frequency dividers which are assigned different divisor values to produce different musical tones at different times. In order to prevent phase synchronism between two simultaneously operating dividers, and thus achieve a rolling phase relationship which is perceived as a chorus effect, divisor values are employed for the two frequency dividers which are not in a whole number relationship. If the two dividers are generating octavely related notes, the divisors used have a ratio not quite equal to the nominal 2:1 value which musical theory requires. Moreover, the exact value of the ratio varies from note to note within each octave so that the rate of phase roll is not monotonously the same for all notes. Alternatively, if the two dividers are both generating the same note, then the divisors used have a ratio which is not quite equal to the 1:1 value which musical theory requires.

Asynchronous tone generator

A reverberation sound producing apparatus includes a nonuniformly tapped delay line, a summing circuit applying an audio signal to the input of the tapped delay line and a feedback path coupling the output taps of the delay line back to its input through the summing circuit. A separate output path couples the reverberation signal from the feedback path to an output amplifier and speaker system. The feedback path is adjusted for minimizing loop gain and the effect of ripple in the frequency response of the delay line while the output path is adjusted for providing a smoothly decaying reverberation signal.

Reverberation system

A tone generator for use with an electronic musical instrument includes a binary counter operated by a binary comparator and a source of clock signals for incrementally advancing or decreasing the state of the counter from a first selected state to a second selected state. The states of the counter control a programmable divider which develops corresponding output tone signals. The counter produces multiple state changes between the selected states so that each individual state change results in a frequency change which is inaudible. The overall effect is to thereby synthesize a tone signal creating the illusion of a continuous pitch change between the pitches corresponding to the selected counter states. The source of clock signals includes a rate multiplier programmed according to the states of the counter to compensate system operation for insuring that similar musical effects defined by corresponding musical intervals are produced in equal time intervals. In a vibrato mode, a second rate multiplier is provided to insure that, for a given frequency output tone signal, different vibrato depths result in vibrato cycles of equal time intervals.

Tone generator for electronic musical instrument with digital glissando,

A time-shared electronic musical instrument is provided with programmable wave-form generating and tone coloring circuits in order to maintain the musical characteristics regardless of pitch. The circuits comprise programmable keyers and wave-shapers, programmable envelope generators, programmable filters, and a programmable voicing selection circuit, in all of which certain characteristics of the output signal are tailored to the frequency of the musical tone.

Programmable circuits for electronic musical instruments

A programmable dynamic filter for use with a time-shared electronic organ or the like includes a filter circuit responsive to a logical state of a control signal for tracking notes generated by the instrument. Means are provided for programming the filter independently of generated notes by selectively adjusting the pulse width of the control signal to achieve desired musical effects.

Programmable dynamic filter

An automatic rhythm generator of an electrical musical instrument including a rhythm pattern generator for rhythmically selecting for actuation different ones of a plurality of instrumentation circuits to be sounded and a strobe pulse generating circuit for establishing the appropriate pulse width of a drive pulse needed by each instrumentation circuit for proper actuation thereof. The rhythm pattern generator circuit selectively enables a plurality of drive gates respectively associated with the plurality of instrumentation circuits during selected ones of a succession of periodic rhythm cycles in accordance with a predetermined rhythm pattern. The strobe circuit is synchronized with the rhythm pattern generator and generates during each rhythm cycle a plurality of strobe pulses on a corresponding plurality of outputs respectively associated with the plurality of instrumentation circuits. Each of the strobe pulses has a width preselected for the instrumentation circuit with which it is associated. The enabled drive gates provide a drive pulse to their associated instrumentation circuits in response to, and having a pulse width proportional to that of, the strobe pulse applied thereto.

Growing community of inventors

Chicago, IL, United States of America

Glenn M Gross