Abstract: In a musical instrument having a solo and accompaniment keyboard apparatus is provided whereby an accompaniment tone color is generated which adaptively complements selected solo tones. The first zero crossing spacing of the autocorrelation function of the solo tones is computed and then used to generate the complementary accompaniment tones.

Abstract: A touch responsive keyboard musical instrument is provided with an array of keyboard switches arranged in octave groups and connected in parallel octaves. A motion transducer is attached to each keyswitch so that a transducer signal is generated corresponding to the motion used to actuate the keyswitches. The keyswitches are sequentially scanned until an actuated keyswitch is detected. At this time the scanning is interrupted until the corresponding transducer signal has reached its peak value. The peak value is used to vary a tonal effect such as a frequency modulation or an ADSR envelope modulation of a tone generator assigned to the actuated keyswitch. The keyswitch scanning is resumed when the peak value of the transducer signal has been measured.

Abstract: In a musical instrument having a solo and accompaniment keyboard apparatus is provided whereby an accompaniment tone color is selected which adaptively complements selected solo tones. The first zero crossing spacing of the autocorrelation function for the solo tone is used to implement a tone selection logic. An effective zero crossing is computed for combinations of available accompaniment tones. An accompaniment tone combination is selected whose effective zero crossing has a maximum value that does not exceed a complemented value of the zero crossing for the selected solo tone.

Abstract: In a musical instrument having one or more tone generators in which a plurality of data words corresponding to the amplitudes of a corresponding number of evenly spaced points defining the waveform of one cycle of a musical signal are transferred sequentially from a note register to a digital-to-analog converter in repetitive cycles at a rate proportional to the pitch of the tone being generated, apparatus is provided for producing tones having independent time-varying harmonic components. A recursive algorithm is implemented which approximates prespecified harmonic-time curves by piecewise segments of exponential functions. Only a small number of stored curve parameters are required to generate the harmonic-time scale factor for a set of harmonic coefficients.

Abstract: In a musical instrument having one or more tone generators in which a plurality of data words corresponding to the amplitudes of points defining the waveform of a musical tone are computed and transferred to a digital-to-analog converter to be converted into musical waveshapes, apparatus is provided for generating tones which are imitative of acoustic signals created by singing or humming. A new tone is obtained by singing into a microphone and actuating a switch. The output waveshapes are generated by implementing a Fourier transform algorithm using a set of harmonic coefficients determined by sampling and processing the signal produced by the microphone.

Abstract: A keyboard operated electronic musical instrument is disclosed for imitating the strummed and solo modes of playing plucked fretted musical instruments. The actuated keys do not directly control the set of tone generators, but are used to automatically select one of a library of chord types which is closest to the actuated keys. A root note is chosen for each selected chord type. The selected chord type is transposed to an open chord spanning the several octaves associated with a guitar-type instrument. The selected tone generators assigned to the transposed open chord are strum keyed in sequence at a rate adaptive to the speed in which successive chords are entered on the keyboard. Provision is made for up-down strumming and to automatically enter a solo tone mode when a sequence of single notes are entered on the keyboard.

Abstract: In an electronic musical instrument having a first and second array of keyboard switches apparatus is provided for providing fill-in notes sounded by tone generators assigned to the first keyboard. The fill-in notes are selected by selecting one of a library of stored chord types which is closest to the notes played on the second keyboard combined with the highest frequency note played on the first keyboard. The closest decision is made by processing the keyed switch data with two sets of matched filters. The chord type decision is made to correspond to a matched filter combination which produces a maximum output response. A root note is also chosen for the selected chord type. The selected chord type and chosen root note are used to provide the fill-in notes.

Abstract: A sequence of timing signals is generated having a time spacing corresponding to the average spacing between successive actuations of a control switch. The system automatically starts a new calculation if the control switch is actuated at least two times with a time spacing less than some prespecified threshold time. The data input process is self-terminated when a time interval equal to the threshold time expires after an actuation of the control switch. The generated sequence of timing signals can be used as the metronome clock for an automatic rhythm generator.

Abstract: A keyboard operated electronic musical instrument with polyphonic portamento and glissando effects in which each key controls one of a number of tone generators through a table of frequency numbers. The frequency transitions are achieved by subtracting the frequency number of a new note from the frequency number controlling the current frequency of an assigned tone generator. A predetermined fraction of the difference is stored in increment registers and added successively to the frequency numbers of the current notes until these numbers are equal to the frequency number of the new note. The addition rate, which determines the frequency transition time, is adjustable by means of a variable frequency time clock. The assignment of the tone generators to the actuated keyswitches is accomplished in a manner which prevents objectionable frequency cross-over transitions even when the number of notes in successive chords is changed.

Abstract: An ensemble effect is produced in a digital tone generator by providing a master data set of words having values corresponding to the relative amplitudes of equally spaced points along one cycle of a waveform of a musical tone in which the fundamental frequency is deleted. These values are read sequentially and repetitively from a memory to produce a first analog tone. A second analog tone is produced by multiplying a data set corresponding to the fundamental frequency by a low frequency sinusoid. The first and second analog tones are summed to yield a musical tone having an ensemble effect.

Abstract: A sliding formant effect is produced in a tone generator of the type in which wave shape data points are sequentially and repetitively read out of a memory at a rate corresponding to the fundamental pitch of a musical tone. The formant effect is obtained by forming the sums or differences between consecutive data points for one waveshape period and storing the new data in memory in response to a formant control signal. Provision is made for advancing or retarding the effective formant cut-off frequency under command of the formant control signal.

Abstract: A reverberation effect is produced in a musical tone generator of the type in which waveshape data points are sequentially and repetitively read out of a memory at a rate corresponding to the fundamental pitch of a musical tone. The reverberation effect is obtained by having a second memory storing waveshape points which are read out simultaneous with those from the first memory. The second data set is scaled by the ADSR envelope function and at selected echo time spacings is pointwise added to the data stored in the first memory. The data read out of the first memory is converted to an analog musical signal having a reverberation effect during the attack or release phase of the musical tone.

Abstract: A keyboard operated electronic musical instrument in which a number of tone generators are assigned to actuated keyswitches. When a keyswitch is actuated, a tone generator is assigned with a musical waveshape selected from a library of waveshapes which are ordered in a predetermined arrangement. The assignment of waveshapes is made in a priority order according to the musical frequencies associated with the actuated keyswitches so that a chorus effect is obtained in which each note of a group of simultaneous notes has its own tone color. The assignment of waveshapes is made in an adaptive manner so that the melody line retains its own distinctive sound even when the number of notes played simultaneously on a keyboard changes. Vibrato effects can selectively be applied to any of the set of waveshapes.

Abstract: A keyboard operated musical instrument with portamento effect in which the portamento keyboard consists of a linear array of keyswitches. The keyswitches are arranged in groups corresponding to each musical note and spaced so that a number of contiguous switches are actuated by each finger in contact with the portamento keyboard. Apparatus is provided for generating a frequency number corresponding to the closest switch actuated by the center of each finger thereby providing polyphonic portamento effects as the finger positions are slid or changed along the portamento keyboard. The frequency numbers are utilized to control the pitches of tones generated by the musical instrument.

Abstract: A keyboard operated musical instrument is disclosed having a portamento effect controlled from a portamento keyboard consisting of a linear array of keyswitches. The keyswitches are arranged in groups corresponding to each musical note and spaced so that a number of contiguous switches are actuated by each finger in contact with the portamento keyboard. Apparatus is provided for generating a frequency number corresponding to the closest switch actuated by the center of each finger thereby providing polyphonic portamento effects as the finger positions are slid along the portamento keyboard. An ADSR generator is used to provide envelope modulations initiated when a new finger has been detected on the slide wire and when a finger has been removed. A priority logic using frequency differences is used to distinguish between new fingers or the changes in position of a finger already in contact with the slide wire.

Abstract: In a keyboard operated electronic musical instrument a detector is provided for measuring the time interval between successively actuated keyswitches. If the time interval is less than a preselected time threshold, the notes are generated with a normal ADSR envelope and if the time interval exceeds this time threshold then the notes are generated with a legato ADSR envelope. Provision is provided to accomodate variations in time when a chord is played. The system will return to the normal ADSR for time intervals greater than that for a second preselected time threshold for notes played with large time separations. The same control signals are provided to control other musical effects such as tone selection, vibrato and portamento.

Abstract: A keyboard operated electronic musical instrument having a number of keyboards in which the loudness balance of the accompaniment keyboards are adaptively maintained at a preselected loudness ratio with respect to the solo keyboard. The loudness balance is automatically maintained as the tone switches are altered and as the number of actuated notes varies on the keyboards. The balance ratio is accomplished by adaptively scaling the harmonic coefficients used in a discrete Fourier transform to generate the tones for the accompaniment keyboards.

Abstract: In an electronic musical instrument apparatus is provided for generating a noise-like signal suitable as source for a variety of musical effects such as the imitation of percussive musical instruments. Noise-like signals of predetermined spectral shape are produced by adding values from a sinusoid table by means of an address control which is incremented randomly according to a decision rule. The decision rule is implemented by a comparison of stored constant values with random values generated by a white noise source. The generated noise-like signals are advantageously employed in digital electronic musical instruments.

Abstract: In an electronic musical instrument apparatus is provided for generating musical sounds having a fundamental frequency which tracks the fundamental frequency of a time varying external control signal. A matched filter is used to generate frequency control signals which are determined by a closeness criterion between the external control signal and an internally generated test signal. Provision is made for offsetting the generated musical sounds for a preselected musical interval from the fundamental frequency of the external control signal.

Abstract: In a musical instrument having one or more tone generators in which a plurality of data words corresponding to the amplitudes of a corresponding number of evenly spaced points defining the waveform of one cycle of an audio signal are transferred sequentially from a note register to a digital-to-analog converter in repetitive cycles at a rate proportional to the pitch of the tone being generated, apparatus is provided for varying the spectral content of the tones in response to a loudness control signal. Loud tones are produced with a greater number of harmonics than those for a soft tone.