Elliot Roberts was one of the youthful entrepreneurs who upended the US music-industry management and promotion establishment in the 1960s.

Through an instinctive understanding of the singer-songwriters then emerging, and with his eyes on the prize, he experienced huge success and helped shape today's music industry.

Roberts, who has died aged 76, is best known as Neil Young's manager for the past 51 years, but he also shepherded Joni Mitchell, Crosby, Stills and Nash, and many others to superstardom.

Born Elliot Rabinowitz in the Bronx, New York, to Jewish emigre parents whose families had fled the Nazis, his father worked as a waiter at the Waldorf Astoria while his mother was a homemaker. Roberts played basketball and went to college on a scholarship but dropped out and tried to make it as a stand-up comedian: his sense of humour was a quality that helped him in his business dealings over the decades.

He attempted a career in acting - and associates would describe him as forever a frustrated actor - before taking a $65 a week job in the mailroom at the New York City office of William Morris Agency (now William Morris Endeavour), the powerhouse US film and music company.

Getting a job in the mailroom was competitive as it proved a stepping stone into the agency, and here Roberts befriended another youth with big dreams, David Geffen. Geffen, a man of great ambition - by 1967 he was managing the precociously talented teenage singer-songwriter Laura Nyro - took Roberts under his wing. "He taught me s*** from the very first day," Roberts said.

Determined to follow suit, Roberts soon found himself looking after the New York talent for managers Bob Chartoff and Irwin Winkler when they resettled in Hollywood. This included several stand-up comedians and the Native American folk singer Buffy Sainte-Marie.

Sainte-Marie played Roberts a tape of a young Canadian singer-songwriter called Joni Mitchell. Impressed, he went to the Cafe Au Go-Go to see Mitchell perform, then approached her offering to his services as manager. The singer cautiously accepted and moved to Laurel Canyon in Los Angeles, and Roberts began hustling on her behalf.

Mitchell then introduced Roberts to two more musicians whom he would take on as clients: her lover David Crosby, recently fired from The Byrds; and, in 1968, a young Canadian called Neil Young. His band Buffalo Springfield, whom Roberts hoped to manage, had seen some success but were on the verge of splitting.

Things got off to a rocky start when Young fired Roberts after he went to the golf course before a concert (when Young wanted his attention), but the two men would soon forge an extremely profitable working relationship. Roberts set about ensuring both Mitchell and Young went from aspiring, critically acclaimed singer-songwriters into two of the most popular rockstars of the 1970s while Crosby, Stills and Nash (and, occasionally, Young) were the biggest selling band in the USA in the early 1970s. Roberts was a hands-on manager, ensuring his artists enjoyed absolute artistic freedom alongside commanding high royalty and performance rates.

Roberts formed the Geffen-Roberts Company with Geffen and together the two men founded Asylum Records, an independent label devoted to singer-songwriters, which merged with Elektra Records in 1972 to form Elektra/Asylum Records. After splitting with Geffen in 1976, Roberts formed Lookout Management. Over the following decades he would also manage America and Bob Dylan, Jack Nitzsche, Talking Heads, Devo, Tracy Chapman and many others.

He and Mitchell ended their working relationship in 1985 after her album Dog Eat Dog proved unsuccessful. Roberts would later note: "Joni taught me everything - not Neil." He would also fall out with his old friend David Geffen in 1983 when Geffen sued Young over the artist's delivery of "uncommercial" albums to Geffen's record label. Roberts was one of the dominant music industry managers and ensured his rockstar clients were treated like gods while stroking their egos so they sometimes believed this was the case.

Forever noted for his long grey hair and a billowing cloud of marijuana smoke, Roberts cultivated a hippie image. Young's biographer Jimmy McDonough described Roberts as "a genius at pushing Young's career" and "difficult, complicated", noting that the Roberts/Young relationship should be seen as akin to that of other infamous artist/managers including Elvis Presley/Colonel Tom Parker. Once, when challenged about the lies he was telling about his artists, Roberts responded, "No, man - they want ya to lie for 'em." He was married several times.

Elliot Roberts, music manager and record executive, born 25 February 1943, died 21 June 2019