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Nov 1979

Volume 66, Issue S1, pp. S1-S89

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back to top Session U. Musical Acoustics III: Electronics in Music
Invited Papers
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Serial‐parallel architecture for real‐time synthesis of music (A)

E. Ferretti

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S41-S41 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Parallel architecture is extremely suitable for the synthesis of music. For example the performance of several instruments at the same time is a directly related task for parallel architecture. Serial architecture on the other hand is ideally suited for optimizing real‐time tasks. The reasons for serial‐parallel architecture are (1) to utilize a single‐type module for computing all tasks in real time, (2) to have a means of adjusting the number of tasks without changing the basic system or violating real‐time requirements, and (3) to have a means of computing time waveforms which require a large amount of transcendental functions for approximating natural sounds. This paper will discuss the issues of system configuration, accuracy, dynamic range of output versus computation, multiple instruments, and modeling of natural sounds for computer music. Some examples of computer music will be presented, and a high‐speed film of a vibrating rubber band will be shown. [This work was supported in part by a private grant from Michael Lay, and use was made of computer facilities in the Computer Science Department.]
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Automatic music performance with computers (A)

A. C. Ashton and R. F. Bennion

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S41-S41 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Developments of the Utah‐BYU music project which have culminated in the design and implementation of a portable computer‐driven music‐generating system capable of interpretive playing of transcribed musical scores will be discussed, and a film depicting concurrent playing and graphing of music will be shown. The portable music system will be used to demonstrate direct interactive performance of a number of musical selections which have been notated in the Utah‐BYU linear music language. Musical parameters such as pitch, duration, tempo, key, voice orchestration, and transposition can be notated for musical performance and can be dynamically modified during the automatic playing of the music. Music generation is accomplished by digital‐to‐analog conversion of stored digital waveforms which are programmably selectable at music generation time. Recordings of a computer‐driven pipe organ will also be played and the organ‐computer interface will be discussed.
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Sound analysis‐synthesis and interactive composition (A)

J. W. Beauchamp

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S41-S42 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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Two distinct projects are under way: (1) Derivation of synthesis models from the analysis of acoustic musical instrument sounds and their use with software‐based synthesis programs on large computers. (2) Development of an interactive computer‐controlled synthesizer system housed in the University of Illinois Music Building. It is hoped that in the not‐too‐distant future these projects will be joined. Current focus in analysis is to estimate the resonant filter characteristics of a wind instrument and use this in conjunction with time‐variant Fourier analysis to derive an excitation signal. This is further processed to reveal a nonlinear distortion function and an index signal. In the simplest case, synthesis over wide dynamic and pitch ranges is possible by merely varying the fundamental frequency and the index signal while keeping the filter and distortion parameters fixed. The interactive system uses a compositionally oriented language called PLACOMP written for the PLATO IV time‐sharing system. A PLACOMP score is translated into numbers which are quickly delivered to a hard‐wired synthesizer. The turnaround time between delivered completion and audible result varies between a few seconds and a few minutes depending on the complexity and length of the composition.
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Dumb ways to play intelligent instruments (A)

M. V. Mathews

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S42-S42 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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In the last five years a new generation of digital instruments has been developed using the new integrated circuit technology. In contrast to previous digital instruments, which were confined to studios, these new instruments are small enough, cheap enough, portable enough, reliable enough, and powerful enough to form a new class of performance instruments. In addition to sound synthesis circuits, they include mini‐ and microcomputers with general computing power and with digital memories. Because of their computational power, we call them intelligent instruments. Musicians must learn very different performance techniques to take advantage of the potential of these instruments. In this paper we review some of the initial ways in which the instruments have been played. We conclude that although many of the performances are interesting, much must be learned before the full potential of these instruments is utilized.
Contributed Papers
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Sequential drum (A)

M. V. Mathews

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S42-S42 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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A sequential drum is described. It consists of a square surface 20″ by 20″ which is hit with conventional drum sticks. Transducers on the surface generate three electric signals each time the surface is hit. One signal is a pulse whose amplitude is proportional to the impact. The other two signals encode the x and y positions of the stroke. The three signals are transmitted to a digital sound synthesizer (Alles machine) which generates a note each time a signal is received. The loudness of the sound is controlled by the amplitude pulse. The timbre of the sound is controlled by the x and y signals. The pitch of the sound is obtained from a score stored in the memory of the digital synthesizer. Each time the drum is struck, the next pitch in the score is played; thus, the desired sequence of pitches is produced automatically by the instrument.
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A study of stretched harmonies (A)

K. T. Marcus, M. V. Mathews, and J. R. Pierce

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S42-S42 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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A class of nonharmonic sounds was synthesized by stretching normal harmonic sounds. Stretching means uniformly expanding the logarithmic frequency ratios between the fundamental frequencies of the tones in a scale and between the fundamental of each tone and its overtones. Stretched passages were studied to see what properties are invariant to stretching. Stretched cords have the same coincidence of overtones as unstretched chords; hence, harmonic perceptions, which depend on overtone coincidence, should be invariant. By contrast, perceptions which depend on periodicity pitch or on the Rameau fundamental bass should be destroyed by stretching. A number of traditional pieces and chords were synthesized in stretched and unstretched forms. These samples were evaluated by (1) informal listening, (2) tests of the identification of the key of the material, and (3) tests of the perception of cadences. Results showed both similarities and differences between stretched and unstretched materials. We believe stretched sounds have perceivable structures that can be utilized in musical compositions.
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Musical spectroscopy I: The real‐time power spectrum in instrument and voice teaching (A)

Charles E. Potter and Dale T. Teaney

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S42-S42 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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We have explored the uses of a real‐time sound color “machine” in the music studio environment. The spectral analysis is performed by a 512 line, 33‐ms FFT instrument; the output of which is sampled every 65 ms at a logarithmically uniform density of 96 points/8va and stored in one of two 512‐ × 10‐bit buffers. The 5‐8va spectra are displayed as graphs one above the other. The rms scale is well suited to a single instrument. A piano keyboard graphic underlines each spectrum. In operation, a model spectrum by the teacher or from a recording is captured by action of a foot switch; the student then observes his own spectrum, running in real time or frozen, on the graph below the model. The spectrometer provides a graphic notation that relates the kinesthetics of production behavior to the acoustic properties of the instrument on the one hand and to the aural penetration of the sound on the other hand. A change of vowel, an alternate fingering, or the influence of a mute is usually enough for the student to get the idea of what the display means to him, and “the machine” then becomes a sort of recording secretary in the performance training dialog.
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Musical spectroscopy II: The sound score in composition and analysis (A)

Robert Cogan, Charles E. Potter, and Dale T. Teaney

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S42-S43 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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In Visible Speech [R. Potter et al., Van Nostrand, New York (1947)] musical applications of a suitably adapted sonogram were foreseen, and Charles Seeger [Musical Quarterly 44, 184–195 (1958)] gave both practical examples of and the theoretical apology for descriptive music writing. In Sonic Design [Cogan and P. Escot, Prentice Hall. New Jersey (1976)] extended music‐spectrographic methods are developed for both analytical and procedural purposes. Our spectrometer (see preceding abstract) generates a simple sound score on a grey‐scale storage monitor. The display is, in effect, proportional notation of the spectral components over a 5‐octave range against a 5‐ to 50‐s horizontal span. The spectral density function. presented at the (z axis) luminance signal, is weighted to give approximately uniform brightness for a sine tone, top to bottom. Klavier or register staff lines are overlaid, and an audiographic equalizer permits modest refinements. Normally read in real time while listening to the music, the sound score can be photographed frame by frame. Examples from diverse musics will be presented.
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