The term "computer music" encompasses a wide range of compositional activities, from the generation of conventionally notated scores using data calculated by the computer, to the direct synthesis of sound in a digital form within the computer itself, ready for conversion into audio signals via digital-to-analog converter, amplifier, and loudspeaker.
There are three basic techniques for producing sounds with a computer: sign-bit extraction, the use of hybrid digital-analog systems, and digital-to-analog conversion. Sign-bit extraction has occasionally been used for compositions of serious musical intent. Little interest persists in building hybrid digital-analog facilities because some types of signal processing, such as reverberation and filtering, are time-consuming even in the fastest of computers. Digital-to-analog conversion has become the standard technique for computer sound synthesis because it is the most versatile method of computer sound generation. Since the sound wave is constructed directly, there are almost no restrictions on sound properties.
To use a computer for music production, the composer or performer first "calls up" from the computer memory the appropriate precompiled program, which is written in a programming language such as FORTRAN, ALGOL, PL/1, PASCAL, BASIC, or COBOL. The program includes various "instruments," i.e., digitally stored musical waveforms, and the operator selects the instruments to use before indicating to the computer in detail—note by note, correct in pitch and timbre—the musical composition to be reproduced.
The computer then translates the instrument definitions into a machine language program, and, if necessary, puts the score into the proper format for processing. After that, the program actually "plays" the score on the instruments, thus creating the sound. The processing of a note of the score consists of two stages: initialization and performance. At the initialization of a note, the values that are to remain fixed throughout the duration of the note are set. During the performance of a note, the computer calculates the actual output corresponding to the sound.
The advantage of digital-to-analog conversion is that the computer can be called upon to assemble the individual sounds into a composition so that the composer need only be concerned with the conception of the piece and the preparation of that conception for the computer. Other advantages are that almost any general-purpose computer can be used for sound generation, and the devices of a synthesizer can be simulated by a computer program. A disadvantage is that the music cannot be altered in real time.
As early as 1843, it was suggested that computers might be suitable for the production of music. Referring to Charles Babbage's "Analytical Machine" (a precursor of the modern computer), Ada Byron King, Countess of Lovelace, suggested that the engine could be used for making music if the necessary information could be understood and properly expressed.
It was not until 1957, however, that computer-generated music became a reality when Max Mathews, an engineer at Bell Labs, began working on computer generation of music and speech sounds. Together with John Pierce and Joan Miller, Mathews wrote several computer music programs, the best known of which is MUSIC V. This program was more than just a software system for it included an "orchestration" program that simulated many of the processes employed in the classical electronic music studio. It specified unit generators for the standard waveforms, adders, modulators, filters, and reverberators. It was sufficiently generalized that users could freely define their own generators. Thus, MUSIC V became the software prototype for music production installations all over the world.
One of the most notable successors of MUSIC V was designed by Barry Vercoe at the Massachusetts Institute of Technology during the 1970s. His program, MUSIC XI, ran on a PDP-11 computer and was a tightly designed system that incorporated many new features, including graphic score output and input. MUSIC XI was significant not only for these advances, but also for its direct approach to synthesis, thanks to improvements in the efficient use of memory space. Thus, MUSIC XI became accessible to a family of much smaller machines that many studios were able to afford. Another major advance was discovered in 1973 by John Chowning of Stanford University, who pioneered the use of digital FM (frequency modulation) as a source of musical timbre.
The most advanced digital sound synthesis is conducted in large institutional installations, most of them in American universities, followed by European facilities. Examples of American installations are Columbia University, University of Illinois, Indiana University, University of Michigan, State University of New York at Buffalo, and Queens College, New York. European facilities include the Instituut voor Sonologie in Utrecht, the Netherlands; LIMB (Laboratorio Permanente per l'Informatica Musicale) at the University of Padua, Italy; and IRCAM (Institut de Recherche et de Coordination Acoustique/Musique), part of the Centre Georges Pompidou in Paris, France.
Computer technology has led to a tremendous expansion of music resources by offering composers a spectrum of sounds ranging from pure tones to random noise. Computers have enabled the rhythmic organization of music to a degree of subtlety and complexity never before attainable. They have allowed composers complete control over their work, if they so choose, even to the point of bypassing the performer as an intermediary between the creators of music and their audience. Perhaps computers' greatest contribution to music is that they have brought about the acceptance of the definition of music as "organized sound."
see also Codes; Film and Video Editing; Graphic Devices; Music; Music Composition.
Joyce H-S Li
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