Beatles fans around the world are paying tribute to the group's longtime producer, Sir George Martin, who died Tuesday at age 90.

Paul McCartney said in a statement, "The world has lost a truly great man who left an indelible mark on my soul and the history of British music." George Martin also left a lasting mark on the art of record production.

Whether horns or harpsichord, so many of the embellishments you hear on the Beatles' songs came from Martin. He wasn't just a good producer, says Grammy-winning producer Nigel Godrich.

"He invented the job," Godrich says. "He invented that thought process of possibility."

Godrich, who produced McCartney's 2005 album Chaos and Creation In The Backyard, says one of Martin's great talents was arranging.

"As an arranger you write the notes," Godrich says. "You listen to the music that exists and you score your parts using the orchestra. So he was very much a musician, countless times on Beatles records." His influence, says Godrich, is "everywhere. It's all over them."

Martin was known for experimenting in the studio. In 1998 he told NPR about the first time the Beatles played him a version of "Please Please Me." He hated it.

"A real dirge," Martin said. "It was very very slow, very boring. I said, 'Look, if you double the speed of that, you might have something, but otherwise, forget it.'" The Beatles took his advice, and "Please Please Me" became a hit.

George Martin's total embrace of music began well before he met the Beatles in the early 1960s. After serving in World War II, he studied composition and orchestration, piano and oboe at London's Guildhall School of Music. He recorded jazz artists, Scottish dance bands and comedy albums.

He brought all of that knowledge and experience to the Beatles. It was Martin's idea, for example, to add strings to "Yesterday" and "Eleanor Rigby."

In his autobiography, Martin said that when John Lennon played him a demo of "Strawberry Fields Forever," it was a "lovely," "gentle" song. He told Lennon he thought it should stay that way. But Lennon wanted to turn it into a heavy rock number, with drums, bass and electric guitars.

Martin lost that battle, at first. The band recorded the song Lennon's way. A week later, Lennon admitted he'd been wrong. Martin said he went on to score "Strawberry Fields Forever" with cellos and trumpet. After much back and forth between him and Lennon — editing different recordings of the song — eventually, Martin told NPR, "Strawberry Fields" became one of his favorite songs.

"I was completely enchanted with that song," Martin said. "I thought the lyrical imagery, and the musical construction, too, were something that I hadn't heard before, and I thought John was going into a wonderfully fertile field."

The best producers find the balance between texture and simplicity. They know when to make a song more robust and when to keep it uncomplicated.

Martin had so many musical ideas and tools at his disposal. He could add layers, experiment with speed, play tape backward, add instruments. But he also knew when to stop.

"If you keep adding colors," he told NPR, "you start getting muddy, and they run, and it gets indistinct. If you can get your effect with a certain degree of cleanliness, then I think it's much better than overloading things."

Small wonder that so many producers would agree with Nigel Godrich, who calls Martin his "spiritual godfather."

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