Abstract: A keyboard operated electronic musical instrument has a number of tone generators each of which creates a plurality of musical tones each having its own independent frequency offset so that a multi-rank ensemble effect is produced. The tones are produced by computing, in real time, sequences of data points using stored sets of harmonic coefficients. Provision is incorporated for producing a musical celeste effect.

Abstract: Two sets of digital tone generators are provided for a musical instrument. The members of the first set of generators create data which represent discrete amplitudes of a musical waveshape corresponding in the time domain to be true musical frequencies played by the musician. The members of the second set of generators create data which represent discrete amplitudes of a different waveshape corresponding in the time domain to frequencies which in general are note selected as true musical frequencies. Provision is made for multiplying the data created by selecting pairs of digital tone generators, one from each of the two sets. The resulting modulated data is converted into analog signals in a form suitable for a conventional sound system.

Abstract: Musical notes having time variant modification of the waveshape are produced polyphonically in a tone synthesizer by computing master and transient data sets, transferring these data to buffer memories, adding the data read out from the buffer memories briefly during a transient time interval and repetitively converting the summed data to waveforms. The master and transient data set are created repetitively and independently of tone generation by computing a generalized Fourier algorithm using stored sets of generalized Fourier coefficients. Circuitry is disclosed for independently applying Attack/Release modulations to the principal tone generated from the master data set and to the transient tone generated from the transient data set.

Abstract: In a digital tone synthesizer, musical tones are created by evaluating a generalized Fourier transform of harmonic coefficients. Tones corresponding to pulse-like waveshapes are simulated by using harmonic coefficient values associated with a pulse waveshape of specified shape. Apparatus is disclosed for producing sets of such harmonic coefficient values wherein each particular set is associated with a selected value of a pulse width parameter. Pulse width modulation tonal effects are achieved by changing the value of the pulse width parameter as a function of time. Means are described for including pulse width modulation as a subsystem of digital tone generators.

Abstract: A musical ensemble effect results when two tones slightly out-of-tune with respect to each other are sounded together upon selection of a single instrument key. Herein, apparatus is disclosed for producing an ensemble effect in a polyphonic tone synthesizer of the type wherein musical notes are produced polyphonically by computing a master data set, transferring data set to buffer memories, and repetitively converting in real time contents of memories to notes. A multiplicity of master data sets are created repetitively and independently of tone generation by computing a generalized Fourier algorithm using stored sets of generalized Fourier coefficients. The phase of such master data sets are generated with time varying phase shifts to provide theout-of-tune ensemble effects. The phase shifted master data sets are combined and transferred to buffer memories from which such data is converted to musical sounds.

Abstract: Musical notes are produced polyphonically in a tone synthesizer or like musical instrument by computing a master data set, transferring data set to buffer memories, and repetitively converting in real time contents of memories to notes. The master data set is created repetitively and independently of tone generation by computing a generalized Fourier algorithm using stored sets of generalized Fourier coefficients. Computations limit tones to audible frequencies, occur at intervals short compared to musical tone periods, and circuitry is included to provide time-varying modulations of the synthesized tonal structure. Synchronizing signals included in the buffer memories provide smooth transition between the master system logic clock and asynchronous tone conversion clocks. A time shared digital-to-analog converter transforms the buffer memory outputs to individual tone channels and provides attack, decay, sustain, release and other amplitude modulation effects.

Abstract: Tone generation in a musical instrument is accomplished by repetitively computing a Fourier algorithm using stored sets of harmonic coefficients. An alterable voice is obtained by optically reading a data card, converting the data to a data format used by the tone generating circuitry, and storing the converted data to be employed as a set of harmonic coefficients. Harmonic coefficient data is encoded on the data card by imprinting columns of opaque areas. The length of each column is measured by sequentially scanning a linear array of light sources. Insertion of the data card in an enclosure automatically initializes the reading circuitry and removing the card causes each opaque data column to be measured in turn and the result converted to a harmonic component.

Abstract: A single amplitude curve generator is time shared amongst a plurality of musical tone generators for controlling their musical shapes. The curve generator creates a wide variety of envelope characteristics by implementing a recursive computation algorithm for selected choices of a single curve shape parameter coupled with the use of a collection of timing clocks used to vary the time intervals associated with the attack, decay, and release regions of the musical tone envelope. Provision is made for forcing the release of a tone generator when a limited number of tone generators have been completely assigned in a keyboard musical instrument and a new note key switch is actuated. Note release signals can be ignored until the amplitude curve generator has completed the attack and decay regions for a given tone generator.

Abstract: In a musical polyphonic tone synthesizer, musical waveshapes are produced by voltage controlled oscillators. The analog frequency control voltages are created by converting stored digital numbers to analog voltages. The selection of these digital numbers and their assignment to a plurality of voltage controlled oscillators is controlled by detecting switches actuated on a keyboard. Provision is made for operating the oscillators over the full frequency range of an electronic musical instrument's keyboard. Automatic tuning means is incorporated to adjust the conversion reference voltage for each oscillator to keep the musical instrument in tune by locking the set of voltage controlled oscillators to a stable reference oscillator. Tuning the reference oscillator thereby tunes the set of voltage controlled oscillators while retaining equal tempered musical frequencies.