FROM the ringtone of a mobile phone to the bleeps and thuds of the latest dance hit, electronically generated sound is now all pervasive. Yet though instruments to make electronic music had been devised as early as 1900, it was not until the 1970s that electronic music was widely heard — and it was played on the keyboards invented by the US engineer whose name became synonymous with the synthesizer, Robert Moog.

As a teenager, Moog (pronounced “Mogue”) had been a devotee of the theremin, the instrument which produces unearthly sounds when the player’s hands are circled around two radio antennae. In 1961, while he was a graduate student, Moog published an article explaining how to build a transistor theremin, and was deluged with more than 1,000 orders for the kit.

Using this financial windfall, Moog — then working on a doctorate in engineering physics at Cornell University — began to experiment with other ways of making and emulating sounds electronically. Mechanical ways of doing this, such as the vast tellharmonium, had been constructed decades before, and in the 1950s RCA had built a laboratory-sized apparatus which required binary-code input — but such instruments were far too cumbersome for any musician to play.

Moog realised that inexpensive voltage-controlled oscillators and amplifiers could be used to alter the pitch and timbre of sounds, as well as their duration and intensity. Any instrument — brass, string or percussion — could be replicated, albeit one note at a time rather than in chords.

Working closely with a music teacher and fellow theremin enthusiast, Herbert Deutsch, Moog took their basic synthesizer to the Audio Engineering Society’s convention in New York in 1964. It quickly attracted attention from several composers, both because at $10,000 it cost a tenth of RCA’s machine and because crucially Moog (who had learnt the piano as a boy) had made the interface with the instrument a conventional keyboard rather than punch cards and dials.

By 1968 Moog had sold dozens of the instruments — their buyers included John Cage and Mick Jagger — and they had been heard on records by the Monkees and on the Beatles’ Abbey Road, but the time-consuming nature of their construction and an innate lack of business sense was threatening to capsize Moog’s company.

Then one of his customers, Walter (now Wendy) Carlos, released an album of Bach’s music recorded entirely on a Moog synthesizer. Switched-On Bach (1968) was a near-overnight sensation; it sold several million copies, introduced electronically generated music to a wide audience and alerted the recording industry to its potential.

Moog capitalised on this success in 1970 by building the Minimoog, the first portable synthesizer. Although it had a range of only three and a half octaves, its size meant that musicians could take it with them on stage or even back home, a flexibility that — when duplicated by tens of thousands of cheaper Japanese models — would ultimately revolutionise pop music, which was now no longer the preserve of those who could play a complex instrument.

From the early 1970s onwards, Moog music began to be heard worldwide, first on film soundtracks such as that for A Clockwork Orange (1971), which was played by Carlos, and later on dance records such as Donna Summer’s I Feel Love (1977). Herbie Hancock took the synthesizer into jazz, while keyboard-based bands — among them Yes and Genesis — rose to new heights of popularity. When they were displaced by Young Turks such as U2 and the Police, the upstarts were building their sound around Moog’s Taurus bass synthesizer. Digitisation would soon overtake Moog’s analogue machines, but like Leon Theremin and Adolphe Sax before him, he had brought something entirely new to music, and not merely one instrument but a veritable orchestra.

Robert Moog was born in 1934 and grew up in Flushing Meadow, New York. His mother was determined that he would become a concert pianist, but he had more interest in his father’s hobby of electronics, and by the age of 15 had already built his first theremin.

From the Bronx High School of Science, where he was bullied for his social awkwardness, he moved on to Queen’s College, New York, to take a degree in physics, followed by one in physics at Columbia University.

Despite the success of the Minimoog, its creator lost control of his company in 1971, first to the entrepreneur Bill Waytena (who relocated it to a former gelatine factory in Buffalo, New York), and then to Norlin Music. Moog was a charming and well-liked man but, as he himself admitted, finance was not his strongest suit. Instead, his principal ambition was to build synthesizers that musicians relished playing, ones that had the feel and resonance of a genuine instrument rather than plastic-covered circuitry.

Accordingly, he remained with Moog Music, as it had been renamed, until 1977, mainly making guitar amplifiers. He then moved to North Carolina, where he set up Big Briar, a company which specialised in other electronic instruments, including theremins. He also taught music technology at his local university.

By the mid-1980s, however, digital synthesizers and the advent of sampling had practically destroyed the market for analogue machines, and in 2002 Moog was able to buy back the firm’s name, and to benefit from the current resurgence of interest in early synthesizer sound, which many musicians feel to be richer and warmer than that produced by computer.

A documentary film about his career, Moog, was released in Britain this year. Moog was the recipient of the Trustee’s Award of the National Academy of Recording Arts and Sciences, as well as the Silver Medal of the Audio Engineering Society of America.

Moog is survived by his second wife, Ileana, and by the five children of his first marriage.

Robert Moog, inventor of the Moog synthesizer, was born on May 23, 1934. He died of cancer on August 21, 2005, aged 71.