Composing tape music by the classic method was neither easy nor free of technical pitfalls. A complex piece had to be assembled from hundreds or even thousands of fragments of tape. Splicing these sounds together consumed a vast amount of time and could also lead to an accumulation of errors and deterioration of the sound. Consequently, substantial efforts were expended to reduce this work load and at the same time improve quality. Music synthesizers were the first product of these efforts. They cannot, however, be regarded as more than an intermediate technological development because of later computer technology (see below).

In contrast to Cahill’s period, by the 1950s the means finally existed to construct full-scale music synthesizers, starting with the RCA Electronic Music Synthesizers, designed by Harry Olson and Herbert Belar, research scientists working at the RCA Laboratories at Princeton, New Jersey. The first machine was introduced in 1955; a second, improved model was turned over to the Columbia–Princeton Electronic Music Center in 1959.

The basic advance of the RCA synthesizer was an information input mechanism, a device for punching sets of instructions into a wide roll of punched paper tape. Composers can at any time during the programming process interrupt this activity to listen to what had been punched, to make corrections, and to edit the material before making a final paper tape that then constituted the “master score” of the composition.

The composer whose name became particularly associated with the RCA synthesizer was Milton Babbitt. He had developed a precisely defined compositional technique involving total serialization (i.e., of every musical element). When he became aware of the synthesizer, he was anxious to use it, because it gave him the opportunity to realize his music more precisely than had hitherto been the case. Among Babbitt’s compositions created with this machine were Composition for Synthesizer (1961), Vision and Prayer (1961), Ensembles for Synthesizer (1963), Philomel (1964), and Phonemena (1974).

In about 1960 a new circuit, the voltage-controlled oscillator (VCO), attracted the attention of engineers interested in electronic music because the frequency of its output signal is proportional to an independently generated input voltage rather than being internally set. The response is immediate because no mechanical couplings or controls are required. Robert Moog was the first to design several types of compact synthesizers of moderate price that supplied an extended range of possibilities for sound manipulation. In addition to VCO’s, which produce sine, square, sawtooth, and triangular waves, the Moog synthesizer contained white-noise generators, attack and decay generators (controlling a sound’s onset and fading), voltage-controlled amplifiers, and band-pass filters and sequencers.

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One major advance in sound manipulation provided by VCO’s is frequency modulation; if the input is a periodic function, the output frequency will vary periodically to provide tremolos, trills, and warble tones. Moog’s synthesizer soon had to compete with several other synthesizers of essentially the same design, the Buchla Electronic Music Box, the ARP, and the later, more sophisticated Prophet 10.

These popular synthesizers eliminate much of the drudgery of tape splicing, but at a price. The range of timbres and processes is more limited because they operate by subtractive synthesis and impose transients that affect all partials (component vibrations) of a complex wave identically. An advantage of a harmonic tone generator built in 1962 by James Beauchamp at the University of Illinois, also from VCO’s, was that it used additive synthesis—i.e., it created sound by combining signals for pure tones (sine waves)—instead of removing partials from a complex signal. It was designed so that each partial of a sound could have its own entry point, its own rise time, and its own decay time. The improvement in tone quality was enormous, because the ear normally expects nuances such as higher partials that decay faster than lower ones. Salvatore Martirano’s Underworld (1965) is a good example of music in which the tape was made largely by additive synthesis.

A composer closely associated with synthesizers is Morton Subotnik, who has produced a series of extended electronic music compositions, starting with Silver Apples of the Moon (1967). These pieces were created on the Buchla synthesizer, and any one of them demonstrates in relatively unmodified form the types of sounds one may obtain with these instruments.

A word should be said about realizations of instrumental music through synthesizers, notably an early, commercially successful album called Switched-on Bach (1968), arrangements made by Wendy Carlos on a Moog synthesizer. The record displayed technical excellence in the sounds created and made the electronic synthesis of music more intelligible to the general listening public. This is useful so long as it is realized that the materials on the record are arrangements of familiar music, not original compositions. (Carlos later created an original electronic score for the science fiction film Tron.)