Music

Music

Computers have had an impact on all segments of the music industry. Specialized hardware and software helps train performers on instruments, such as piano and guitar, and assists with instruction in music theory, ear training, and general musicianship. Computers are used to help create new compositions and analyze existing ones. Computers can also be used to produce the raw sounds of music through synthesis and sequencing software and hardware.

Since the late 1960s, most composers and publishers have used computer notation and typesetting programs instead of engraving and hand copying to make printed scores and parts. The use of digital technology for music production, including recording and editing, and for playback is almost universal. Music can be heard and exchanged over the Internet, and computer-generated music is heard in film scores, television commercials, popular music, and classical music concerts.

However, the most significant impact of computers may be the increased ease with which people are able to participate in the making of music. Performers can create and "play" their own instruments without years of traditional training, for example, and can generate recordings and distribute them over the Internet outside the traditional studio system.

Sound Synthesis and Recording

The term "electro-acoustic" music is used to describe music in which the sounds are produced, changed, or reproduced by electronic means, or synthesized, rather than being produced by naturally resonating bodies such as the vocal cords. In traditional electronic music, sound is generated by devices such as oscillators that produce an electrical signal. Processors, such as mixer, filter, and reverberation modules, can then modify the signal.

This process is called analog synthesis because the electrical signal produced by the synthesizer is a nearly exact representation of the waveshape of the actual sound. In analog recording, the microphone converts the waveshape of the sound into an electrical signal that is pressed into the groove of a record. As the needle wiggles along this picture of the waveshape, it is converted back into an electrical signal. The analog representation of sound is on a continuous scale; like the sweep second hand on a watch, it is able to represent any two points and all possible points in between.

Digital synthesis and recording are based on the idea that it is possible for the continuous waveshape of a sound to be represented by a series of numbers. This process is known as quantization. Computers are ideal machines for generating and storing those numbers. However, special hardware is required: digital to analog converters (DACs) are needed to translate numbers into electrical voltages and analog to digital converters (ADCs) are used to translate voltages into numbers.

The digital representation of sound is on a discrete scale of steps, like a digital watch that can indicate 1:00 and 1:01 but nothing in between. The waveshape of a sound is specified, or sampled, at evenly spaced points along the wave. The frequency with which the samples are taken is the sampling rate. The higher the sampling rate, the more exactly the waveshape is represented and the higher the fidelity of the resulting sound. A general principle is that the sampling rate must be at least two times the frequency of the highest sound to avoid distortion.

Figure 1 shows in simple terms how the representation of a waveshape changes if Sample Rate 1 is cut in half.

Another important issue in digital sound representation is the size of the unit used to store samples. Small units, such as eight bits , can store a limited range of numbers. Many values must be rounded off and information is lost. Achieving high fidelity requires a big memory, however. Representing four seconds of sound in sixteen-bit units requires approximately 700,000 bytes .

Digital synthesis is limited by the time required for the computer to calculate the numbers for each sample. If the time needed is greater than the sampling rate, the sound cannot be produced in real time; the values must be stored in a file that can be played back once all the calculations are complete. This makes experimentation, variation, and modification difficult.

History

As early as 1843, Ada Byron King, Countess of Lovelace, suggested that Charles Babbage's Analytical Engine , a forerunner of the computer, might be used for music. In 1957 this vision was realized in two very different ways. Lejaren Hiller and Leonard Isaacson wrote a computer program that composed the Iliac Suite using the laws of chance and basic rules of music composition. This program generated a score that was played by human musicians.

The pioneering work in computer music was done using software synthesis. This is the most flexible and precise method because synthesis programs can be run on general-purpose computers.

Early music synthesis programs such as MUSIC III (1960) were written using the concept of unit generators, like the modules of analog synthesizers. In the 1960s and 1970s, most computer music was produced at universities and research institutions. Software synthesis became more widespread in the late 1980s with the introduction of low-cost, good quality, digital to analog converters for personal computers and graphical user interfaces (GUI).

By 2000 software synthesis programs included two categories: (1) graphical instrument editors in which the user simulates using an analog synthesizer by clicking on icons on the display screen; and (2) synthesis language programs in which the user specifies sounds by writing text that is interpreted by the program.

Researchers also designed special-purpose hardware for music functions. This path led to commercial digital performing instruments, including the Synclavier (1976) and the Fairlight (1979), which are widely used by performers. However, the flexibility of these machines is limited by the fixed nature of their circuitry, which cannot be modified to perform new functions. Lack of standardization was a problem in the 1970s and early 1980s. Development of the Musical Instrument Digital Interface (MIDI), released in 1983, provided a standard protocol for exchanging musical information among different brands of computers and synthesizers.

see also Analog Computing; Apple Computer, Inc.; Babbage, Charles; Digital Computing; Lovelace, Ada Byron King, Countess of; Microcomputers.

Cheryl L. Cramer

Bibliography

Dodge, Charles, and Thomas Jerse. Computer Music: Synthesis, Composition and Performance, 2nd ed. Belmont, CA: Wadsworth, 1997.

Hofstetter, Fred T. Computer Literacy for Musicians. Englewood Cliffs, NJ: Prentice Hall, 1988.

Howe, Hubert S., Jr. Electronic Music Synthesis. Englewood Cliffs, NJ: Prentice Hall, 1975.

Roads, Curtis. The Computer Music Tutorial. Cambridge, MA: MIT Press, 1996.