John Maus of the Walker Brothers, the neighbour who taught Carl Wilson how to play Dick Dale-style surf guitar, believed he experienced the birth of Pet Sounds in the Wilson family living room in 1961. "There was an ocean of music in that house," said Maus. "Audrey, the mom, played boogie-woogie on piano. Murry, the dad, played his jazzy compositions. Carl wanted to be Chuck Berry." In the background, said Maus, Brian was forever toying with his Wollensak T-150, the two-track reel-to-reel recorder acquired for his sixteenth birthday in 1958. Legend has it Brian spent endless hours deconstructing Dick Reynolds' intricate vocal arrangements for The Four Freshmen. Maus recalled Brian dissecting something else: pop music's first-ever concept album, Gordon Jenkins' 1946 song-and-narration suite Manhattan Tower. "It seemed old hat to me," said Maus. "But Brian was hung up on its eccentricities — car horns, street sounds. On reflection, I guess, he was seeing the bigger picture. He was seeing a widescreen movie, while the rest of us were in love with Chuck Berry on the TV."

It's well-worn history now that the Beach Boys came together when Brian's school friend Al Jardine suggested they form a band and Dennis Wilson urged Brian and cousin Mike Love to write songs eulogising teen surf culture. "Those songs filled a gap," says Mike Love. "After Elvis joined the army and Little Richard the ministry, rock 'n' roll lapsed. Brian, like me, was a jock. We were competitive. We saw our moment and came up to the plate. We offered a different kind of music: do-wop meets Dick Dale." From the time they signed with Capitol Records in the summer of 1962 until the spring of 1964, the Beach Boys scored five hit albums and five top-20 singles.

Then the Beatles arrived. They changed not just music but culture itself, impacting fashion, humour, advertising, and movies. Unlike the United States, Germany hadn't shucked off the fury of Elvis — the musical voice the Beatles assimilated there was a mixture of rage rock and Schlager, a ballad form of docile sentimentalism. Back in Liverpool, they honed their skills in marathon cellar club sessions and borrowed compositional ideas from Brill Building writers like Goffin and King, Bacharach and David, Phil Spector and Berry Gordy's Motown.

For three months after their American arrival, the Beatles swept the Billboard charts, with eight songs in the top ten at one time. What they presented was formidable, but the Beach Boys rose to the challenge, producing a resounding number one in July with "I Get Around." Carl Wilson recalled: "I was the biggest fan of the Beatles. As soon as I heard them, I thought, They'll be tough to top. But Brian was growing so fast. Surfer Girl. In My Room. The Warmth of the Sun. Don't Worry Baby. He was blossoming like a flower, experimenting with chromaticism, chord inversions, and intervals no one else was trying."

The so-called British Invasion, said Les Maguire, keyboardist of Gerry and the Pacemakers, was a siege of copycats. "The Dave Clark 5 were copying the Beatles. The Rolling Stones were aping R&B. Herman's Hermits were doing novelty numbers like Disney's Sherman Brothers." Les, like Brian Wilson, had an inclination for orchestration. "I was jazz-oriented. I saw the limitation of three-chord beat songs and felt the pop scene of 1964 was a dead end. Three chords and mohair suits were cost-effective, so our moment passed, and the Brit Invasion ended."

Glen Campbell observed the waves of alternating fads, both on the road and in the studio as part of the legendary Wrecking Crew. In the winter of 1965, he was summoned to begin recording what would become Pet Sounds.

In Mike's absence on the road, Brian's choice of lyricist was a new acquaintance, copywriter Tony Asher. They bonded over Stella By Starlight, a forties staple by Victor Young and Ned Washington that Asher played on piano to invoke an atmosphere of high romance. In a literary sense, the lyrics formed a classic Bildungsroman, a coming-of-age tale. The suite opens with the childlike optimism of "Wouldn't It Be Nice," then moves through self-doubt and yearning to passion and escape — culminating in the anguish of loss in "Caroline, No."

Al Jardine believes the Beach Boys' history pivots on the comprehensive experimentation of Pet Sounds. In the era before digital recording, Brian used bicycle bells, chopsticks, and found objects to create an otherworldly soundscape.

Musical history records that the Beatles' Rubber Soul influenced the creation of Pet Sounds, provoking Brian's desire to create an album without fillers. History also records Pet Sounds' reciprocal influence on the Beatles, prompting the experimental range of Revolver and laying the groundwork for Sgt Pepper's Lonely Hearts Club Band. But Pet Sounds did much more than inspire the Beatles. It was, as Mike Love asserts, an unarguable high point in the evolution of pop, giving birth to what is today regarded as the advent of the album era.

It is ironic that, though Pet Sounds sold half a million copies in its first year, an administrative error meant it was not granted gold record status until 2000. In America, artists universally applauded it. In Britain, a plethora of the best listened and dove into radical experimentation. In the months that followed came The Moody Blues' Days of Future Past, The Zombies' Odessey and Oracle, The Kinks' Face to Face, Donovan's Sunshine Superman, and The Bee Gees 1st — all albums whose significance has accrued massively over the years.

In the opinion of Geoff Emerick, the Beatles' engineer, the dynamism that made the music of the sixties historically transformative belonged to two artists: "I credit the Beatles with reinventing rock 'n' roll after Elvis and the Beach Boys for reinventing pop after the Brit Invasion. Between them, they rewrote the rule book."