Geoff Emerick, the Beatles studio engineer who entered the music business in his mid-teens and by his early 20s had helped make history through his work on such landmark albums as "Revolver" and "Sgt. Pepper's Lonely Hearts Club Band," has died. He was 72.

Abbey Road Studios, home to the Beatles and many other recording artists, confirmed the death Wednesday and vowed to ensure that Emerick's legacy lives on. Colleague William Zabaleta told Variety that Emerick collapsed and died Tuesday while they were talking on the telephone. He said Emerick had suffered from heart problems in recent years.

Paul McCartney, in an online tribute Wednesday, wrote that Emerick "had a sense of humor that fitted well with our attitude to work in the studio and was always open to the many new ideas that we threw at him. He grew to understand what we liked to hear and developed all sorts of techniques to achieve this. ... We spent many exciting hours in the studio and he never failed to come up with the goods."

A London native fascinated by music and technology from an early age, Emerick wasn't widely known to the general public, but he was an invaluable part of the Beatles' legacy as they became increasingly ambitious and experimental in the studio and helped transform rock music into an art form. He was on hand during the Beatles' early EMI sessions, in 1962, as an assistant under lead engineer Norman Smith. He was promoted after Smith left to become a producer in the mid-1960s.

"Geoff Emerick used to do things for the Beatles and be scared that the people above (in the EMI hierarchy) would find out," producer George Martin later said for a 1990s Beatles documentary. "Engineers then weren't supposed to play about with microphones and things like that. But he used to do really weird things that were slightly illegitimate, with our support and approval."

His first album as Beatles engineer was "Revolver," the 1966 release that marked the band's full embrace of such studio effects as backward tape loops and double tracking. In one famous story that Emerick told on numerous occasions, he came up with a unique solution when John Lennon told him he wanted his voice to sound like "the Dalai Lama singing from a mountaintop 25 miles away from the studio" on the tripped out "Tomorrow Never Knows." Emerick found a way to process Lennon's voice through a revolving speaker to produce a landmark of psychedelic music.

"That sort of won John over," Emerick said in 2016.

On Wednesday, Lennon's widow, Yoko tweeted that she was "shocked" by Emerick's death.

"He was the best engineer," Ono wrote. "Not only was he the best engineer, he was very, very kind."

Ringo Starr wrote in a statement, "With him and George Martin they helped us to step up on Revolver. He will be missed."

He had other innovations on the Beatles' most complex and anticipated album, "Sgt. Pepper," which came out in 1967. He enhanced the sound of Starr's drums on "A Day In the Life" by loosening the skins and wrapping a microphone in a tea cloth and placing it in a glass container. Under his supervision, McCartney recorded bass lines after the rest of a given track was done, an unusual sequence at the time.

By 1968, the Beatles had tired of studio tricks and were otherwise growing apart, in part because of Lennon's relationship with Ono. Emerick became frustrated during the recording of the double "White" album and briefly quit.

"The expletives were really flying," he later told Beatles historian Mark Lewisohn. "There was one instance just before I left when they were doing 'Ob-La-Di, Ob-La-Da' for the umpteenth time. Paul was re-recording the vocal again and George Martin made some remark about how he should be lilting onto the half-beat or whatever and Paul, in no refined way, said something to the effect of 'Well you come down and sing it.' I said to George 'Look, I've had enough. I want to leave. I don't want to know any more.'"

He returned for the Beatles' final studio sessions, for "Abbey Road," and worked with McCartney on his solo "Band On the Run" album, for which Emerick's engineering brought him a Grammy. He also won engineering Grammys for "Sgt. Pepper" and "Abbey Road" and received a lifetime achievement honor in 2004. Other artists he worked with included Cheap Trick, Elvis Costello, Jeff Beck, and, early in her career, Judy Garland.

In 2006, he published his memoir "Here, There and Everywhere," which received some criticism at the time from Beatles fans for its apparent bias toward McCartney at the expense of the other band members, especially George Harrison.

"A lot of people think I'm being hard on George," he told CNN at the time. "But I haven't glossed anything over. It's my memory, it's the way I perceived, from my situation, the way we went through those albums."

On Wednesday, McCartney wrote that Emerick visited him earlier this year while he was recording his "Egypt Station" album, which came out last month.

"We kept in touch through the years and our phone calls or messages always gained a giggle or two," McCartney wrote. "He was his usual cheerful friendly self (earlier this year) and gave me the thumbs up to the mixes we played him. I'll always remember him with great fondness and I know his work will be long remembered by connoisseurs of sound."

AP National Writer Hillel Italie contributed from New York.