Giant Steps - how Gentle Giant star made John Lennon's bed rock

When they saw a bed in Abbey Road's studio three, the three Shulman brothers couldn't resist using it as a trampoline. "We'd just finished a recording session and were trying to see who could jump higher," admits singer Derek, then known as Simon Dupree of Simon Dupree & The Big Sound. "The bedsheets were all over the place." Then the Lennons turned up. "John said, 'Jesus Christ! What bulls*** is this?', and then Yoko told us to get off but in more colourful terms. It was embarrassing to say the least; I blamed my older brother Phil for encouraging me. We didn't hang around for a conversation. Luckily the Beatles never knew we spent more time on their instruments than on their bed."

When their band went Top Ten in 1967 with psychedelic single Kites, their manager booked them a three-hour recording session to create a follow-up. "We put together a crazy thing called We Are The Moles which we released as The Moles," says Derek, 78, with a smile. "George Martin produced it." They then left a tape in a London luggage locker and sent the key to open it to music weekly Melody Maker saying that Parlophone would release it. "By the time it reached the Top 50 everyone was talking about it. There were rumours that it was the Beatles with Ringo singing. It was on course to be another smash hit. Then Syd Barrett [of Pink Floyd] decided it was getting out of hand and blurted out that it was us. He wasn't a very pleasant person..."

Parlophone had signed the 5-piece blues and soul band the year before, launching a career that uniquely would encompass Elton John, progressive rock, and the Kray twins. "Elton, or Reg as we knew him, was fantastic," says Derek, whose memoir is published on Friday. "He was our keyboardist on a 1967 tour and was and is a great friend. He was very instrumental in our development, encouraging us to listen to Miles Davis, Spirit, and Frank Zappa" - all of whom proved influential for their next band. "Dudley Moore played on one of our tracks. So many people became friends. It was fantastic. Abbey Road felt surreal. You'd see Cliff Richard and Pink Floyd drinking tea and eating chips in the canteen...I felt like the Forrest Gump of the music business."

They opened for Californian superstars the Beach Boys in May 1967. "We loved their music but they were disappointing. Their backup band hadn't been allowed into the UK because of Musicians Union rules, so they had to play on their own and they weren't good. Dennis Wilson wasn't much of a drummer and they wouldn't even talk to us. They were like that with everyone on the bill, including Helen Shapiro."

The Portsmouth-based quintet broke up in 1969. "We were stymied by being pushed as a pop band; and we didn't like being on the scampi and chips club circuit. Everyone played it back then, even Joe Cocker, but it was soul-destroying - you could hear people ordering drinks at the bar."

They did an abrupt about-face and became something completely different - progressive rock pioneers Gentle Giant whose complex, experimental music attracted fans ranging from Jethro Tull's Ian Anderson to a generation of hip hop giants. Anderson recalls the perfectionist siblings having after-show "murderous fraternal screaming matches over a missed semi-quaver."

Rap superstar Travis Scott had a US Top 3 smash with Hyaena, which sampled their 1974 track Proclamation, De La Soul's Friends sampled The Advent Of Panurge, Madvillain used their Funny Ways on Strange Ways, and Run The Jewels recycled Knots for Legend Has It. "About twenty of our songs have been sampled," says Derek, who was feted by Jimmy Fallon's house band The Roots. "Their drummer, Questlove, told me, 'You guys have got a ghetto pass'." It completes a circle - Derek's first band were inspired by the music of black America; now black American musicians are inspired by them. But why? He thinks it's because they wrote intricate pieces involving point-counterpoint dynamics rather than meandering space operas and quasi-symphonies.

Glasgow-born Derek's family moved to Portsmouth when he was a toddler. His father Louis was a pro jazz trumpeter and the house was full of musical instruments and often jamming musicians, so of them junkies. "Dad encouraged us to play, and be good at it." His late younger brother Ray, a gifted violinist, was set to join the National Youth Orchestra, but was persuaded to join their band instead. Radio Luxembourg and the American Forces Network had turned Derek on to R&B and the blues - "Stuff you couldn't hear on the BBC light programme; pirate radio was the thing for our generation." At 17, he told his careers master he was going to be a rock star. "He said I'd never make and should aim for a profession. Two years later I was on Top Of The Pops."

Gentle Giant played arena shows across Europe and North America selling "several million albums around the world; we were a cult, but we were a big cult." And still are. Their remastered version of their 1977 live album Playing The Fool went Top 15 in May this year. Their greatest high was headlining Los Angeles's Shrine Auditorium in '77, when the 8000-strong audience refused to leave. "We did the encore, no one left, then another; the lights went up and still they wouldn't leave. We'd run out of songs so our drummer suggested we play Wilson Pickett's In The Midnight Hour, which we used to do in rehearsals. Even then they wouldn't go..."

More notorious fans included Wilf Pine, whose criminal mob ran the Isle of Wight. Wilf, an associate of the Kray Twins with New York mafia links, took Simon Dupree & The Big Sound "under his wing, and promoted our shows locally; we were semi-naive about it. Once Wilf asked Phil to look after a bag of jewels for a few days because the heat was on with the local police."

In 1970, Pine's cronies steered Gentle Giant to sign with a company run by Don Arden and Patrick Meehan, who also managed Black Sabbath. It ended badly. "Our tour manager worked for them, and had started managing Judas Priest. He told us they had got us a US deal with a £150,000 advance. Well, we hadn't seen any of that. The house and cars we had, weren't ours, we had nothing; we were ripped off just like Ozzy and Sabbath were. And it was the same for Edgar Broughton and the Groundhogs, although we weren't fleeced as heavily as they were because they knew the Krays liked us. We did a deal with Capital Records and got our catalogue back. Sabbath didn't get theirs back for years. "Two weeks later, we were told that the tour manager who'd told us about the money had 'committed suicide'."

Punk bands were prog's sworn enemy, but Derek was simply baffled by them. "The Clash's producer invited us to watch them record their first album," he recalls. "They were a bit s***. We were musicians, we could play, and they were struggling with basic chords. It was bizarre. In retrospect I loved London Calling and Rock The Casbah but back in early 1977, The Clash were made by their producer" - fellow Scot Mickey Foote. For Gentle Giant's last US tour, they invited Canvey Island pub rock band Dr Feelgood to support them. "They got the sh***ty end of the stick from our fans. A shame. They booed them as harshly as Black Sabbath fans had once booed up."

A couple of years after breaking up in 1980, Derek followed another calling. As a record company executive, he signed Bon Jovi - convincing them to adopt that name. He also helped resurrect AC/DC's then flagging career and went on to champion and work with bands like Pantera. "It was important for me that the bands were innovators; leaders in their field. Every band I signed, I got my hands wet with, leading the charge. Like Gentle Giant, they did our own thing."

He loved Amy Winehouse, found Paul Weller "difficult and demanding", and rates Noah Kahan but says, "Everything I hear on the radio is the same. It has nothing to do with soul or heart or creativity. Pop songs are designed for ten seconds of TikTok. "Success is about the music and being honest, authentic, and truthful. Be who you want to be."

*Giant Steps by Derek Shulman is published on Friday, November 14.