Abstract: Apparatus for generating an output signal having a frequency and duty cycle controllable in response to a pair of binary control words. The apparatus includes a pair of counters which are alternately enabled for counting high frequency clock pulses for respective time durations determined according to the two binary control words. A bi-stable device is controlled by the counters for developing the output signal which alternates between two levels for time durations corresponding to the time periods during which the two counters are enabled. The frequency and duty cycle of the output signal are therefore controllable by suitably adjusting the values of the two binary control words.

Abstract: 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.

Abstract: A circuit for generating alternating repeat keying signals in an electronic keyboard musical instrument includes a clock, a logic circuit responsive to the keys of the instrument and to the clock for producing an alternating sequence of logic signals corresponding to each of the keys, the phase of the sequence corresponding to each undepressed key being the same as the phase of the sequence corresponding to the previous key and the phase of the sequence corresponding to each depressed key being opposite that of the phase of the sequence corresponding to the previous key and a plurality of output gates each developing a keying signal in response to the depression of a respective one of the keys and the logic signals of the corresponding sequence assuming a predetermined state.

Abstract: A variable frequency oscillator for an AC power supply having programmable, multiple phase outputs comprises means including a rate multiplier for generating a clock signal having a selectively controllable frequency and one or more AC signal producing stages responsive thereto. Each AC signal producing stage includes a memory storing a quarter-cycle sinusoidal waveform segment in amplitude sampled form and an address counter responsive to the clock signal for alternately addressing the memory in forward and reverse directions for producing a continuous sequence of half-cycle sinusoidal segments, an output circuit inverting every other one of the half-cycle segments.

Abstract: A programmable electronic musical synthesizer includes a memory controlling a plurality of parameter circuits according to a selected group of stored parameter signals for producing a desired timbre of sound. A memory override system is responsive to manual operation of each of a plurality of control knobs for overriding a corresponding stored parameter signal and coupling an externally derived input signal to the associated parameter circuit. The memory override system thereby conveniently enables one or more selected parameter circuits of the synthesizer to be manually controlled by a performer while the other parameter circuits are simultaneously controlled from memory.

Abstract: 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.

Abstract: An electronic musical instrument having combined monophonic and polyphonic sound producing capabilities includes a keyboard simultaneously operating a monophonic tone signal generating circuit and a polyphonic tone signal generating circuit. The tone signals produced by the tone generating circuits are combined and coupled through a single signal processing stage and therefrom to an output speaker. A gate signal for enabling the monophonic tone signal generating circuit and for operating the signal processing stage is derived at the output of a detector circuit which is responsive to the presence of an audio output from the polyphonic tone signal generating circuit.

Abstract: A variable rate tuner is one in which the rate of change of tuned frequency with respect to tuning shaft rotation varies automatically as a function of the shaft rotation speed. In this tuner the circuitry is completely digital, including a shaft encoder which puts out shaft velocity and shaft direction signals. A digital multiplier multiplies or divides the shaft velocity signal. A counter selects the multiplication factor as a function of shaft velocity. The multiplied velocity signal then increments or decrements a frequency-determining quantity, depending upon whether the shaft direction is such as to increase or decrease the tuned frequency.

Abstract: 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.

Abstract: An apparatus for measuring the moisture content of a soil sample at selected depths is disclosed. Light is conducted from a source via a fiber optical cable to a soil probe which is inserted at selected depths into a bore hole formed in the soil sample. Light from the source and reflected light from the soil sample is conducted via fiber optic cables to a reflectometer, which determines reflection factors of the soil sample at three selected infrared wavelengths of a water absorption band. Means are provided to compute the moisture content of the sample at the selected depths from the measured reflectance factors.

Abstract: 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.

Abstract: A method of daytime imaging in a range of thermal wavelengths (3-5 microns) which includes specularly reflected solar radiation. Mathematical processing serves to separate the thermal and specular reflection components based on Fresnel's equations which relate the thermal component to three variables: the total radiation intensity; the degree of polarization of the total radiation; and the degree of polarization of the specular reflection component. The first two of these variables may be measured by means of a photometer which is scanned across a target area, and a suitably oriented polarizing filter. The third variable can be calculated as a function of two other quantities: the angle of incidence of sunlight on the target object and the index of refraction of the target object. The first of these two quantities is calculable from time and geographical position data, while the second can be estimated with sufficient accuracy.

Abstract: This is an electronic organ drawbar circuit in which selection of the footage volumes is accomplished by means of a switch matrix; and sets of footage/volume correlations so chosen are stored in a memory. Another group of switches is used to select among several different memory fields, so that various sets of footage/volume data can be stored while another set of data is in use, and each stored set can be recalled for subsequent re-use.

Abstract: A hammer strike line adjuster for use with a grand piano comprises a metallic, generally U-shaped bracket, a worm gear rotatably received within a pair of aligned apertures formed in the side walls of the bracket and a shift pin having a first end secured to the piano key frame assembly and a second end engaging an annular recessed portion of the worm gear for movement together therewith. The apparatus, which is disposed between the piano key frame assembly and treble arm and underlying the piano key block, is operative for accurately adjusting the position of the piano hammer strike line in response to rotation of the worm gear.

Abstract: An automatic rhythm generator for use in an electronic organ is made more efficient, from the standpoint of rhythm pattern storage, by use of a zero suppression technique. Null instructions, the sole function of which is to allow a clock interval to pass without sounding an audible beat, are eliminated entirely from storage, and thus do not consume any memory capacity. In order to skip the necessary silent clock intervals before the next audible beat, each beat instruction which is stored at a memory address may include an encoded skip instruction commanding a number of clock intervals to be skipped before passing on to the next beat instruction at the next memory address. Alternatively, the skip instruction, in a stored program instrument, may come from software. In either case, the skip instruction controls a programmable frequency divider, which causes clock interval skipping by dividing down the clock frequency to a lower rate before it reaches the memory address counter.

Abstract: 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.

Abstract: 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.

Abstract: An electronic apparatus cabinet assembly comprises a generally U-shaped extrusion having an interior mounting rail disposed near an open end thereof and a deck member secured between the legs of the extrusion. An RFI sealing material is disposed overlying the mounting rail which receives a lid member having dimensions slightly smaller than the open end of the extrusion. Upon forcing the lid member into compression against the sealing material and mounting rail, some of the sealing material is forced upward from the interstice between the lid member and the extrusion forming a joint having a high integrity RFI seal.

Abstract: 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.

Abstract: The disclosure describes improved apparatus for use in an electronic musical instrument having a keyboard including a group of keys corresponding to the notes of a musical scale. Electronic circuitry is used to generate simultaneously with respect to each of the keys first and second electrical tone signals, the repetition rates of which are detuned with respect to each other so that the sound of a chorus is simulated.The disclosure also describes circuitry useful in an electronic musical instrument having a keyboard including twelve keys corresponding to the twelve notes of a chromatic musical scale. The circuitry generates simultaneously a first series of twelve tone signals corresponding to a first tempered scale and a second series of twelve tone signals corresponding to a second tempered scale different from the first tempered scale.