Showing papers in "Computer Music Journal in 1987"

M and Jam Factory

Abstract: M (Fig. 1) and Jam Factory (Fig. 2) are the first software packages published by Intelligent Music, a company founded by composer Joel Chadabe to provide a commercial outlet for interactive composing software (Chadabe 1984) and intelligent instruments. M and Jam Factory, commercially available since December 1986, run on Apple Macintosh computers equipped with a MIDI interface (Chadabe and Zicarelli 1986, 1987). Both M and Jam Factory are programs that, through the use of graphic and gestural interfaces, provide an environment for composing and performing with MIDI. The resulting environment, characterized by controls that offer immediate feedback in modifying an ongoing process, is quite analogous to the control panel of an airplane. Indeed, one of the early models for the programs was Fokker Triplane, a flight simulation program for the Macintosh.

An Expert System for Computer-Assisted Composition

Abstract: Computers offer opportunities for style imitation (Hiller and Isaacson 1959; Winograd 1968; Lidov and Gabura 1973) and afford novel solutions to problems in music composition. They have been successfully used in automated music (Hiller and Isaacson 1959), algorithmic composition (Fry 1984), and as stochastic probability generators (Xenakis 1971), to name a few. Artificial intelligence systems have created serious interest for music analysis (Roads 1985a) and composition (Cope 1987). "Experiments in music intelligence" (EMI) was begun (1984) as an interactive partner for the author. Initially viewed as an analysis tool for generating extensive lists of motivic patterns, it quickly grew into an imitative projector of possible next intervals of given phrases. From these early programs grew a large set of functions that allowed for style dictionaries and syntax rule applications. Rather than avoiding the author's own biases, the system developed explicitly around them. These included projections of linguistic parselike networks for phrase structures, intensely rigorous motive replications, and a proclivity for analyzing music by intervals rather than by pitch.

History and Principles of Microtonal Keyboards

Abstract: As real-time computer music performance systems become more widespread, the question of controller design becomes increasingly pertinent. The flexibility of pitch afforded by computer technology suggests the use of new input devices optimized for playing in arbitrary tuning systems. In particular, keyboards are well-suited for polyphonic playing, and there is a legacy of historical microtonal keyboards that can serve as models for controller design. Several motivations for using a microtonal keyboard in computer music can be discerned. The obvious use is for live performance-microtonal music no longer needs to be primarily restricted to tape music on the one hand and to the musiciancraftsman who constructs special acoustic instruments on the other. An equally compelling motivation drives the composer of microtonal music. The real-time aural feedback provided by such a device can open the door to experimentation with many tuning systems whose harmonic resources might otherwise remain untapped. A flexible device for real-time pitch control could also be of use in psychoacoustic research. The greater portion of this article outlines the history of microtonal keyboards, with a view towards establishing the most useful design principles. The final section considers how these principles can be adopted for synthesizer control. A programmable keyboard is particularly useful, allowing a variety of tuning systems and key layouts; software written by the author for such a purpose is described. With such a device, different keyboard layouts can be used to match the tuning system and the nature of the musician's usage, as will be explained. History and Principles of Microtonal Keyboards

Tuning: At the Crossroads

Abstract: The arena of musical scales and tuning has certainly not been a quiet place to be for the past three hundred years. But it might just as well have been if we judge by the results: the same 12/2 equally tempered scale established then as the best available tuning compromise, by J. S. Bach and many others (Helmholtz 1954; Apel 1972), remains to this day essentially the only scale heard in Western music. That monopoly crosses all musical styles, from the most contemporary of jazz and avantgarde classical, and musical masterpieces from the past, to the latest technopop rock with fancy synthesizers, and everywhere in between. Instruments of the symphony orchestra attempt with varying degrees of success to live up to the 100-cent semitone, even though many would find it inherently far easier to do otherwise: the strings to "lapse" into Pythagorean tuning, the brass into several keys of Just intonation (Barbour 1953). And these easily might do so were it not for the constant viligance on the part of performers, and the readily available yardsticks for equal temperament provided by the woodwinds to some extent, but more so by the harp, organ, or omnipresent piano (inexact standards that they may in truth be). Yet this apparent lack of adventurousness is not due to any lack of good alternatives (Olson 1967; Backus 1977; Lloyd and Boyle 1979; Bateman 1980; Balzano 1980) or their champions. Indeed an experienced musician would have to be preposterously naive, sheltered, and deaf (!) not to have encountered at least a name or two like Yasser (1975) or Partch (1979), or in an earlier era, Bosanquet, White, Brown, or General Thompson (Helmholtz 1954; Partch 1979). These pioneers were certainly not known for their shy reticence on behalf of their various tuning reform proposals. Nearly all built or

Two Essays on Theory

Abstract: For more than two thousand years it has been a well-known fact that two pitches that have a simple frequency relationship between them (such as 1:2, where one frequency is twice as high as the other) form a harmonic interval (an octave in this example). However, it is undisputable that a given interval with a complex numerical relationship in the direct vicinity of another, more harmonic interval, falls into the pull of the stronger one, as it were. It thus operates as an approximation (for instance: an interval with the frequency relationship of 100: 199 is only 0.7% smaller than an octave and is therefore heard as an octave); this "bending into place" is the topic of this text.

Paratactical Tuning: An Agenda for the Use of Computers in Experimental Intonation

Abstract: Several factors have significantly affected, and perhaps more importantly, limited, the choice and usage of intonational strategies in music. Recognition of the existence of these limitations, as well as a discussion of procedures adopted to circumvent them, may help us to design computer-based tuning systems with greater flexibility and increased experimental possibilities. One of these limiting factors is the classification of instruments into two categories: those of fixed pitch (like keyboards) and those of variable pitch (like unfretted strings). Even though most instruments do not securely fit into either category (like the fretted strings, the keyed winds, or countless other instruments from around the world), it has been a consistent tendency among composers, theorists, and musicians to assume that they do. Or it has been assumed that their idiomatic usages preclude the possibility of performance in the mode of the other category. For example, it is generally conceded that string quartets and vocal ensembles develop sophisticated intonational adjustment procedures because of the nondiscrete pitch scale available to them, while other ensembles of so-called fixed-pitch instruments (those with a presumed limited set of pitches available, like the piano) have a simpler set of procedures for intonational performance. (In modern Western music, this is assumed to be twelve-tone equal temperament.) Although most contemporary Western performers on fixedpitch instruments have developed methods of extending the pitch resources of the instruments' twelve-tone equal design, these methods are not

Spectrum Analysis Tutorial, Part 1: The Discrete Fourier Transform

Abstract: This tutorial is an outgrowth of a course in signal processing given by Julius O. Smith at Stanford University in the fall of 1984 (see Smith 1981, as well). It provides an elementary mathematical introduction to spectrum analysis. This is the first of two parts. In part one, the discrete Fourier transform is introduced and analyzed in depth. In part two, some fundamental spectrum analysis theorems and applications are discussed. The only mathematical background assumed is high school trigonometry, algebra, and geometry. No calculus is required. Familiarity with summation formulae, complex numbers, and vectors is helpful, although not essential.

Spectrum Analysis Tutorial, Part 2: Properties and Applications of the Discrete Fourier Transform

Abstract: In part one of this tutorial (Jaffe 1987), we introduced the discrete Fourier transform (DFT). To review, the DFT takes a waveform as input and produces as output the spectrum of that waveform. One way to understand this process is to consider the samples of the waveform as a vector and to see the DFT as the projection of this vector onto a set of complex sinusoidal basis vectors. In this manner, the DFT produces a sequence of spectral components equally spaced in frequency, with a length equal to that of the original waveform. Each element of the spectrum is a coefficient of the projection given by the inner product of the waveform with one of the basis sinusoids. This coefficient can be represented in polar coordinates to give the amplitude and phase of the corresponding sinusoid. The equation for the DFT is:

Computer Realization of Extended Just Intonation Compositions

Abstract: If a superposition of two or more periodic frequencies within the audible spectrum can be expressed in terms of simple ratios of the form fl /f2 = n/m (where n, m are integers), the subjective perception of the degree of blend or consonance of the superposition is inversely proportional to the magnitude of the integers required to represent it. Thus, the Just perfect fifth (3/2) is perceived as being more consonant than the Just major third (5/4), which is more consonant than the septimal minor third (7/6), and so on. A superposition is considered "perfectly consonant" when there is a coincidence of all harmonic spectra (unison and octave), "consonant" when the frequencies are separated by an interval greater than the critical band (a frequencydependent minimum separation between activated regions along the basilar membrane beyond which "beating" or "roughness" is no longer perceived), and "nonconsonant" or "dissonant" when the frequencies differ by about 5%-50% of the corresponding critical bandwidth (Roederer 1979). An intonation system based on ratios thus allows for the establishment of musical structures re-

A Natural Language System for Music

Abstract: As computer music systems become more complex and sophisticated, there is often a corresponding increase in the level of expertise required to use them effectively. As a result, a musician typically spends a lot of time "learning the system," instead of making music. What is needed is a user interface that musicians can use with little or no formal training, yet is sufficiently powerful to handle all of their requests. This paper describes a natural language interface for musical applications that is both easy to use and sophisticated enough to handle complex programs. The system described is designed to be tailored to a number of computer music applications ranging from musical score editing and Musical Instrument Digital Interface (MIDI) recording to digital editing and automated mixer/patch-bay control. In its initial application, it serves as a "front end" to eled (Decker et al. 1986), which serves as a score editor and MIDI sequencer.

The Primula Machine

Abstract: The Primula Machine is a very compact microprocessor-based system for music composition, sound synthesis, and live performance. This system can be considered a personal music computer. It is inexpensive (in relation to the facilities offered), easy to transport, and easy to learn how to use. Its sound quality and timbral variety are good, and it is a flexible composition tool. This machine was designed bearing in mind that music and programming are similar phenomena: both a program and a piece of music are first planned and then executed. The name "Primula" was taken from the name of the software that controls the ma-