Their debut album, Emerson Lake & Palmer, included souped-up versions of Bartok's 1911 piano suite Allegro barbaro and the first movement of Janacek's Sinfonietta.
Released in November 1970, it reached No4 in Britain and No18 in the United States album charts and went gold mainly thanks to Lucky Man, an acoustic ballad Lake had written at the age of 12 and which was subsequently released as a single.
In the next seven years the band released six platinum albums, including Tarkus (1971); Pictures at an Exhibition (1971, from a live performance at Newcastle City Hall); Trilogy (1972); and Brain Salad Surgery (1973).
ELP, as they became known, were the first band to make the synthesiser integral to their performances, and it was Emerson, widely regarded as the best virtuoso keyboardist on the rock scene, who drove their characteristic sound. The experience of hearing him "pummelling Bach half to death", one fan recalled, seemed like "revenge for those of us who had endured years of compulsory piano lessons".
The band also pioneered today's stadium spectaculars with over-the-top shows full of flying pianos, fireworks and giant armadillos firing polystyrene "snow".
In 1973-74, when they took 36 tonnes of equipment on a world tour, only the Stones, The Who and Led Zeppelin were bigger concert draws.
Things did not always go to plan. Once the armadillo fired the polystyrene into Emerson's grand piano, forcing a 20-minute hiatus while roadies dismantled the instrument and used a vacuum cleaner to remove the "snow".
Emerson's on-stage theatrics - including stabbing his Hammond organ with two Hitler Youth daggers (to wedge down specific keys during solos), playing the organ upside down or backwards, and using a special rig to spin his grand piano over the stage - also took their toll. Once, the piano suddenly stopped mid-spin, breaking his nose; on another he sustained cuts and bruises when the instrument, which had been rigged up with fireworks, exploded prematurely.
In his "musical biography" of ELP, Endless Enigma (2006), Edward Macan identified two rival ideological streams emerging in rock music of the early 1970s - the "utopian synthesism" of groups such as ELP, which sought to transcend musical genres and raise the intellectual calibre of rock, and "blues orthodoxy", which saw blues as the root of all authenticity and was well represented among rock critics - particularly the British ones - of the time.
As a result, even as they filled stadiums, ELP were rubbished by the rock press, John Peel dismissing them as "a waste of talent and electricity" and Robert Christgau describing them as "as stupid as their most pretentious fans" and assigning a C minus to their album Trilogy.
Hearing him 'pummelling Bach half to death' ... seemed like 'revenge for those of us who had endured years of compulsory piano lessons'.
"If you looked up the word 'pretentious' in the dictionary, you could well find 'Emerson, Lake and Palmer'," as Carl Palmer later admitted.
It was often said to be the advent of punk that proved their undoing. But in fact by the time the Sex Pistols hit the London stage in 1976, ELP already seemed old hat and the band themselves were worn out. A 1977 world tour with an entourage of 115 people, including a $20,000-a-day full orchestra and choir, had to be drastically cut when tickets did not sell. Soon after the release of Love Beach (1978), their only album not to make the top 40, ELP broke up.
Emerson was born on November 2, 1944 in Todmorden, Yorkshire, and grew up in Worthing, West Sussex.
His father played the piano by ear, and as a child Keith tried to emulate him. One of the first records he bought was the jazz and classical musician Dave Brubeck's Take Five. From the ages of 8 to 12, he had piano lessons, but claimed to be largely "self-taught", his teachers only having imparted "the basic rudiments of music - like where to find the middle C".
But by his mid-teens he was playing with local bands, and by his late teens had moved to London, where he joined the band V.I.P.'s and later Gary Farr and the T-Bones. In his 20s, he formed the trio (and briefly quartet) the Nice, in which he began developing his crossover blend of classical, jazz and rock - and his extravagant onstage persona. The band soon gained a strong live following and achieved commercial success with an instrumental rearrangement of Leonard Bernstein's America.
The Hammond organ had been Emerson's instrument of choice but that changed when he heard the 1968 album Switched-On Bach by Walter Carlos, who performed classical pieces on the then-new synthesiser.
The early-generation analog synthesisers, created by Robert Moog, had featured on the Beatles' Abbey Road in 1968, but it was Emerson, with ELP, who turned it into a central rock instrument.
"I suppose it was rather like the early airplane pilots," he recalled in an interview in 1996. "We were really dealing with equipment that wasn't designed to fly. The early modular synthesisers ... were very prone to changing keys and picking up radio signals. They would even catch transmitter calls from passing taxis when we would be playing."
ELP were always a strange combination of high and low art, and sometimes even band members found it hard to define their identity.
Their original title for the album Brain Salad Surgery (which contained versions of William Blake's Jerusalem and a cerebral Alberto Ginastera piano piece) was Whip Some Skull on Yer while, much to the annoyance of its designer, HR Giger, a penis had to be airbrushed from the album cover. Though critically derided, many fans considered the album to be their best.
After 1978, ELP made several, mostly half-hearted, comeback attempts, yielding two more albums. Meanwhile Palmer joined the super-group Asia, Lake began a solo career, and Emerson produced a solo album and wrote several film scores, including for Dario Argento's Inferno (1980) and the Sylvester Stallone thriller Nighthawks (1981).
In the early 2000s he toured in the US, Britain, Europe and Japan with the Keith Emerson Band.
His autobiography, published in 2003, was Pictures of an Exhibitionist.
It was a fair description of his stage persona but in person Emerson was courtly and disarmingly softly spoken. In 2005, Castle Records put out a two-disc compilation of his works, Hammer It Out.
In July 2010, ELP reunited in London for a 40th-anniversary set - their first live gig in 12 years - at the High Voltage Festival. Emerson's last concert was last July at the Barbican, where he performed a tribute to Moog on a synthesiser alongside the BBC Concert Orchestra.
Through the years, Emerson consistently won the Overall Best Keyboardist award in the annual Keyboard Magazine readers' poll. He was also honoured by the Smithsonian Institution, with Moog, for his pioneering work in electronic music.
Yet he seemed to regret the synthesiser revolution he had helped start. "People were worried when we came out that synthesisers would eventually take over, and in fact it has actually happened," he said in 1992. "Now there's a reliance on sequencing and everything in music, and sadly there's a loss of real players."
Emerson was inducted into the Hammond Hall of Fame in 2014.
In 1969, he married his Danish girlfriend, Elinor, with whom he had two sons, but the marriage later ended.
Emerson, who had recently had surgery for an intestinal growth, was found dead by his long-time girlfriend Mari Kawaguchi at his home in Santa Monica, California, on March 10.
Police have confirmed that no one is being sought in connection to the death.
