Abstract: A concatenated coding system consisting of a (255,223) Reed-Solomon outer code and a convolutional inner code is provided with either a block of preinterleaved frames or an interleaver of frames in a block of data symbols to be coded in the outer decoder. By interleaving, errors are constrained to occur in only one symbol in a frame, which can be corrected by the Reed-Solomon outer decoder. After transmission and inner decoding, the data symbols are deinterleaved for outer decoding. Instead of preinterleaving at the source, or interleaving before inner encoding, the frames of data symbols may be interleaved at the receiver after inner decoding and then combined with the inner decoded check symbols for outer decoding. The outer encoder is a bit-serial Reed-Solomon encoder with programmable interleaving, and the inner decoder is a Viterbi decoder.

Abstract: Two pipeline (255,233) RS decoders, one a time domain decoder and the other a transform domain decoder, use the same first part to develop an errata locator polynomial .tau.(x), and an errata evaluator polynominal A(x). Both the time domain decoder and transform domain decoder have a modified GCD that uses an input multiplexer and an output demultiplexer to reduce the number of GCD cells required. The time domain decoder uses a Chien search and polynomial evaluator on the GCD outputs .tau.(x) and A(x), for the final decoding steps, while the transform domain decoder uses a transform error pattern algorithm operating on .tau.(x) and the initial syndrome computation S(x), followed by an inverse transform algorithm in sequence for the final decoding steps prior to adding the received RS coded message to produce a decoded output message.

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 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 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 electronic musical instrument is disclosed wherein the number of tone generators is less than the number of keyswitches in a keyboard array of keyswitches. If all the available tone generators have been assigned to actuated keyswitches, the actuation of an additional keyswitch causes the oldest tone generator to be assigned to the newest keyswitch. The assignment action does not depend upon the release of any keyswitch. A phase addition means is used to remove the oldest tone generator so that release key clicks are not generated.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators which are assigned to actuated keyswitches. Musical tones having an anharmonic overtones structure are produced by generating a number of component waveshapes each having a different fundamental frequency. These component waveshapes are summed to produce a single tone. Each component waveshape has a spectral content of a preselected subset of non-zero harmonic coefficients. The various components have mutually exclusive selection for the non-zero harmonic coefficients.

Abstract: A keyboard operated electronic musical instrument is disclosed in which an independent monophonic tone synthesizer is operated from the same keyboard that controls the generation of tone from a polyphonic tone generation system. The highest frequency note is assigned to the monophonic tone synthesizer and all other actuated keyboard switches are assigned to the polyphonic tone generation system. The detection of the highest note is initiated each time that a keyswitch changes from an unactuated to an actuated state. An alternative arrangement is to assign the lowest frequency note to the monophonic tone synthesizer.

Abstract: A keyboard operated electronic musical instrument is disclosed which has a number of tone generators that are assigned to actuated keyswitches. The tone generation is produced by sequentially and repetitively accessing a memory containing a set of data points which define a period of a preselected musical waveshape. Apparatus is described whereby a plurality of tone generators are implemented by each one selecting data points read out of the memory in response to a comparison logic.

Abstract: Apparatus is described to control the starting phase of a new tone for a keyboard operated electronic musical instrument having a number of tone generators. An interval detection subsystem is used to determine if a new note is separated by a given musical interval, such as an octave, from a currently generated musical tone. If the prespecified separation is detected the new tone generator is initialized so that its starting waveshape phase is equal to that of its related interval neighbor. Provision is incorporated to shift the new tone generator by a random frequency offset to phase unlock the octave intervals.

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: 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 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: 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 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 electrical tone generator apparatus is provided for automatically selecting one of a library of chord types which is closest to a chord fingered on a fretted string instrument. The closest decision is made by processing the fingered fret input data by a set of matched filters each of which corresponds to a member of the library of chord types. The chord type decision is made to correspond to the matched filter producing the maximum output response. The selection between chord types yielding equal responses is resolved by priority logic based upon the frequency of chord usage. A root note is chosen for each chord type. Note keying data is generated from the selected chord types which is transposed to the correct musical pitches in response to the chosen root note. The note keying data is grated by an automatic rhythm generator and the output is used to actuate electronic musical tone generators.

Abstract: In an electrical keyboard musical instrument apparatus is provided for automatically selecting one of a library of chord types which is closest to a chord played on the instrument. The closest decision is made by processing the actuated keyswitch data by a set of matched filters each of which corresponds to a member of the library of chord types. The chord type decision is made to correspond to the matched filter producing the maximum output response. The selection between chord types yielding equal responses is resolved by priority logic based upon the frequency of chord usage. A root note is chosen for each selected chord type.

Abstract: A complementer for floating point binary numbers utilizes two digital logic decision rules selected by the value of the power of the input number. The first decision rule is selected for an input power of -1 and constructs a power and mantissa determined by the binary sequence form of the input mantissa. The second decision rule is selected for input powers less than -1 and constructs a mantissa determined by the binary sequence form of the input mantissa and the value of the power. The complemented power is set to a -1 value. The complementer is advantageously employed in digital electronic musical instruments.