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: Apparatus is disclosed whereby an electronic musical tone generator is controlled in response to a musical instrument using mechanically vibrated strings. A bank of digital note filters is associated with each string to find the closest true musical note frequency corresponding to the vibration frequency of the string. The filters operate by computing the autocorrelation function of the string's vibration waveshape and then performing a Fourier transform to obtain the identification of the closest true musical note. An efficient and simple implementation is disclosed for an analog-to-digital signal conversion, the computation of the autocorrelation, and the Fourier transform. Provision is made for introducing frequency changes corresponding to a pitch bend in the vibration frequencies of the string.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators each of which is assigned to an actuated keyswitch. Musical waveshapes are generated by a computation using a set of harmonic coefficients. Apparatus is described for generating the set of harmonic coefficients in response to a preselected set of increment number values wherein this set is less in number than the number of harmonic coefficients in a set. The generation of harmonic coefficients is accomplished by computing linear slope variations of groups of coefficients.

Abstract: A keyboard operated musical instrument is disclosed in which musical tones having a variable spectral content are produced from waveshape data values that read out from a stored set of waveshape data points. A second set of data values is computed at the same rate as the rate for sequentially reading out the stored set of data values. A data select means periodically selects a sequence of the read out waveshape data points followed by the selection of a sequence of points from the second set of data values. The selected data points are converted into audible musical tones. Provision is made for varying the shape of the second set of data values in a time dependent fashion as well as to vary the time for which each data set is selected.

Abstract: A tuning indicator is disclosed in which the octave, note within the octave, and a tuning error is displayed for a musical tone played into a microphone. A bank of digital octave filters, a bank of digital note filters, a bank of digital cent filters operate simultaneously and in parallel to analyze the fundamental frequency of the musical tone. The filters operate by computing the autocorrelation function of the input signal and then performing a Fourier transform to obtain the frequency analysis data. An efficient and simple implementation is disclosed for the computations including the analog-to-digital signal conversion, the computation of the autocorrelation function, and the Fourier transform.

Abstract: A keyboard operated musical instrument is disclosed in which the number of tone generators can be less than the number of keyswitches in a keyboard array of keyswitches. A binary-tree search is programmed to search subsets of the keyswitches to find keyswitches that have been actuated. The subsets are selected in an adaptive fashion which minimizes the search time required to detect and identify all the actuated keyswitches. A modular assignment subsystem is described whereby tone generators are assigned to actuated keyswitches according to a predetermined priority logic.

Abstract: A keyboard operated electronic musical instrument is disclosed in which musical tones are created by reading out preselected data values stored in a waveshape memory. A transformed sequence of these data points is generated such that a variable delay exists between the transformed sequence of data points read out of the memory. The selectively delayed sequences of points is combined with the original points to generate musical tones having an ensemble-like musical effect. Provision is made for varying the delay in a periodic cyclic fashion using a period the same as that for the stored data in the waveshape memory.

Abstract: A keyboard operated musical instrument is disclosed in which dual musical tones are created by reading out data values stored in a waveshape memory. Waveshape data values are read out alternately by two memory addressing circuits. One memory addressing circuit addresses out waveshape data values at a constant memory address advance rate corresponding to the fundamental frequency of an actuated keyboard switch. The second memory addressing circuit addresses out waveshape data points at a time variant memory advance rate. The two sets of read out waveshape data values are combined to produce a dual musical tone.

Abstract: A keyboard operated musical instrument is disclosed in which musical tones are created by reading out data values stored in a waveshape memory. The number of stored data points is reduced by storing the data values in segments corresponding to one-half of the number of data points for a period of a waveshape. By using synthesized data having a symmetry about the midpoint, the second half of the waveshape is recovered by a forward and backward memory address read of each waveshape segment. After reading each segment a predetermined number of cycles, an abrupt jump is made to the next segment of waveshape data points. The fundamental frequency of the tone is varied in a temporal manner by changing the memory advance rate of reading waveshape data out of memory in response to a frequency offset data corresponding to each segment of the waveshape data. An alternative embodiment is disclosed for a tone generator in which the musical waveshape is computed in real time from stored sets of harmonic coefficients.

Abstract: A keyboard operated musical instrument is disclosed in which musical tones are created by computing waveshapes from a set of harmonic coefficients. Tones with time variant spectra are obtained by scaling each harmonic coefficient in response to a stored set of scaling numbers. An efficient scaling implementation is described which changes the harmonic coefficients by increments of a predetermined ratio. The tone generation system provides a significant reduction in the number of stored numbers in comparison with a simple stored waveform tone generator.

Abstract: A keyboard operated musical instrument is disclosed in which the musical tones are generated by reading out data values stored in a waveshape memory. The number of stored data points is reduced by storing the data values in segments corresponding to one-half of the number of data points for a period of a waveshape. By using synthesized data having a symmetry about the midpoint the second half of the waveshape is recovered by a forward and backward memory address read of each waveshape segment. After reading each segment a predetermined number of cycles, an abrupt jump is made to the next segment of waveshape data points.

Abstract: A keyboard operated musical instrument is disclosed in which the musical tones are generated by reading out a sequence of data values stored in memories. A first memory stores the musical waveshape for the attack and decay phases of the musical tone. One of a plurality of memories, each storing a period of a different waveshape, are selected by means of a touch response signal generated by the manner with which a keyswitch is actuated. At the end of the decay phase the waveshape selected by the touch response signal is read out sequentially and repetitively and is substituted for the data stored in the first memory. A means is provided to minimize the transient created in the transition between data read out of the first memory and the selected second memory. Provision is also made for a touch response loudness effect.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators that are assigned to actuated keyswitches. Musical tones are produced by computing a master data set from an interpolated sequence of harmonic coefficient values. The master data set points are read out sequentially and repetitively from a memory and converted into an audible tone. A plurality of harmonic coefficient memories are used to store preselected sets of harmonic coefficients. In response to a timing clock, the harmonic coefficients from a cyclically chosen pair of harmonic coefficient memories are selected. A tone having a time variant spectra is produced by using a time variant interpolation between the selected pair of harmonic coefficients.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators that are assigned to actuated keyswitches. Musical tones are produced by computing a master data set which defines the data points corresponding to a period of a musical waveshape. The master data set points are read out sequentially and repetitively from a memory and converted into an audible musical tone. Circuitry is provided whereby the master data set is computed from a time sequence of harmonic coefficients which is modulated to produce a musical tone having a time variant spectra.

Abstract: In a musical instrument in which a plurality of data words corresponding to the amplitudes of a corresponding number of evenly spaced points defining a cycle of an audible musical waveform are transformed at an average rate corresponding to the fundamental frequency of the tone being generated, a computation means is provided to produce musical tones having an ensemble effect. The computation means comprises a multiplicity of interpolation calculations whereby a sequence of interpolated waveshape points are obtained from two different waveshapes whose data points are addressed from waveshape memories at different memory advance rates.

Abstract: In a musical instrument in which a plurality of data words corresponding to the amplitudes of a corresponding number of evenly spaced points defining a cycle of an audible musical waveform are transformed at an average rate corresponding to the fundamental frequency of the tone being generated, a frequency generator is provided using a single clock source for selectively producing the entire frequency range of selected musical notes. A non-integer frequency generator is implemented which periodically adds a frequency number, corresponding to an actuated keyswitch, to itself in an accumulator. The integer portion of the accumulator content is used to address out waveshape values stored in a memory. The decimal portion of the accumulator content is used to select the time at which either the current read out waveshape data value or a previously read out waveshape data value is converted into an analog signal by means of a digital-to-analog converter.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators each of which is assigned to an actuated keyswitch. The generated musical waveshapes are transformed to produce tones having a time variant spectra by processing the waveshapes with a time variant masking function.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators that are assigned to actuated keyswitches. The generated musical tones are selectively varied in tone color by multiplying tone data values by a masking function. A library of masking functions are stored and are selected by a control signal. Musical tones with time variant harmonics can be generated.

Abstract: A keyboard operated musical instrument is disclosed in which the speed of successively closing a first and second key contact on a keyboard switch is measured by means of a key detect and assignor system. A fast response time is obtained by scanning only the second set of key contacts which correspond to a previously detected closure of a first key contact. The measured closure speed can be used to control various musical effects such as the initial loudness in a touch responsive tone generation system. A method is also disclosed for measuring and utilizing the speed with which a keyswitch is released.

Abstract: A keyboard operated musical instrument is disclosed in which a musical tone having an extended range of harmonics is produced by combining two waveshapes at different fundamental frequencies. The first waveshape has a fundamental frequency corresponding to an actuated keyboard switch and has a spectrum containing a maximum of Q harmonics. The second waveshape is created by a single side-band modulation of two orthogonal musical signals each having a maximum of Q harmonics and has a phase coherence with the first waveshape. The second waveshape is generated at a frequency which is Q+1 greater than the fundamental frequency of the first waveshape. The first and second waveshapes are combined to produce a musical tone which has an extended range of harmonics.