BRIAN Wilson tells the story of how Don Henley once came backstage after a concert. The Eagles co-founder arrived clutching his copy of Pet Sounds, the Beach Boys’ classic 1966 album, and told Wilson how much their music had inspired him when he was younger.

Keen to have Wilson autograph the album, he watched as Wilson picked up a Sharpie and wrote: “To Don – thanks for all the great songs.” Henley turned to leave but Wilson called him back and, grabbing the record, crossed out “great” and replaced it with “good”.

Henley took it well.

Wilson could get away with it. After all, this is the man who created Pet Sounds – identified as the second greatest album of all time by Rolling Stone magazine in 2012 – and who co-wrote so many Beach Boys classic songs and shaped their distinctive sound.

The anecdote also sheds light on the esteem in which many rock legends themselves hold Pet Sounds, which was created when Wilson was just 23, and was released in the States on the same day in May as Bob Dylan’s Blonde on Blonde.

Paul McCartney has described God Only Knows, the album's centrepiece, as the greatest song ever written (it was interesting that his daughter, Stella, should have chosen it as one of her Desert Island Discs recently), and the Beatles themselves were influenced by the album to create Sgt Pepper's Lonely Hearts Club Band, their own high watermark.

Wilson himself, now 75, is embarking on a substantial tour to mark the album’s 50th anniversary. After bringing both that and the follow-up "lost" Smile album to Glasgow’s Clyde Auditorium at the start of the new century, he returns next month – to the Kelvingrove Bandstand, specifically – to play the songs from Pet Sounds.

By 1966 the Beach Boys had had four years of remarkable success with their catchy, harmony-laden songs about surfing, cars and girls. Wilson, however, had grown weary of the incessant touring and promotional duties that came with being in such a successful group. For all that he had achieved, he wanted to explore his creativity even more fully. “I wanted to spend more time in my house, writing songs at home, so I told the guys I was gonna stop touring,” he told the BBC Two Classic Albums programme on Pet Sounds last year. But further impetus had come in December 1965 when he had listened to the Beatles’ Rubber Soul, an album he saw as “definitely a challenge for me”.

On that same programme, author and music journalist David Wild said Wilson’s decision to quit the road and spend more time in the studio “is one of the most profound moments in rock history, because it really is when Brian Wilson, I think intuitively, decided that he was going to be an artist … he found that his instrument was the recording studio”.

Wilson co-wrote the songs with Terry Asher, who at the time was working in the advertising industry. Wilson called in some of LA’s most formidable session musicians, collectively known as the Wrecking Crew (among them drummer Hal Blaine, bass player Carol Kaye and, contributing guitar, one Glen Campbell, who also played on Sinatra’s Strangers in the Night and Elvis Presley’s Viva Las Vegas). The recording process was an exceptionally demanding one, but out of it emerged a remarkable album. Wilson’s own website describes it as “the emotional autobiography” of its youthful “auteur”.

Author Pete Doggett, in his authoritative pop history book, Electric Shock, says Pet Sounds was “teenage pop’s first viable rival to the thematic records of [country singer] Jean Shepard and Frank Sinatra”. Wilson, he adds, “retained just enough of the group’s natural effervescence to sustain their commercial appeal amidst his stunningly complex and baroque instrumental arrangements”.

Wilson himself knew instantly that he had made a record that would last. “I thought it was one of the greatest albums ever done,” he wrote in I Am Brian Wilson, his 2016 memoir. “I thought it was a spiritual record. When I was making it, I looked around at the musicians and the singers and I could see their halos. That feeling stayed on the finished album.” He had made a similarly telling observation in 1990: “I dreamt I had a halo over my head. This might have meant that the angels were watching over Pet Sounds.”

By this time Wilson had been experiencing mental health issues, the beginning of what author Michael Gray once termed “a long slide into stupor and derangement”. Wilson’s many problems have been chronicled extensively; but, in the light of everything he has endured, it’s good to see him on the road again, celebrating the album one last time.

Despite their age, the songs have not dated. God Only Knows, the album’s centrepiece, remains “sublime”, in the opinion of Jim Fusilli, author of The Beach Boys’ Pet Sounds. He is surely right. The song and its stately, yearning intro – all French horn and staccato piano chords – is utterly perfect for the final, emotional scene in Richard Curtis’s 2003 rom-com Love Actually, when families and lovers are reunited at Heathrow’s arrivals hall.

In his liner notes in a two-CD reissue of Pet Sounds (released last year at the same time as a five-disc deluxe boxset, containing outtakes, live recordings and alternate mixes), journalist David Fricke said he could hear its “textural invention, symphonic drive and confessional intensity” in everything from late 1960s/early 1970s R’n’B, in the “cathedral resonance” in the guitar work of U2’s the Edge, in Radiohead’s groundbreaking album Kid A and in Jeff Buckley’s 1994 studio album Grace. That is quite a legacy.

Paul McCartney has acknowledged the impact on Sgt Pepper. “The biggest influence, as I’ve said a lot of times,” he said in The Beatles Anthology, “was the Beach Boys’ Pet Sounds, and it was basically the harmonies that I nicked from there. Again it wasn’t really avant-garde, it was just straight music, surf music – but stretched a bit, lyrically and melodically.”

Keith Richards of the Rolling Stones was less impressed, recalling in his autobiography a few years ago that he thought Pet Sounds was “all a little bit overproduced for me, but Brian Wilson had something”.

Journalist Barbara Ellen, looking back on an album she belatedly grew to love, wrote last year: “Amid the myriad musical styles (psychedelia, jazz, choral, classical, avant garde) and notorious cacophony (barking dogs, trains, bells), it details the fragile arc of a relationship, rising euphorically (Wouldn’t It Be Nice?), struggling and doubting (That’s Not Me), then inevitably falling (I Just Wasn’t Made for These Times). Shimmering at the centre was God Only Knows – a pop hymn that still sounds akin to wings ripped from an angel.”

Jon Savage’s verdict in his book, 1966: The Year the Decade Exploded, summarises for many people the reasons why Pet Sounds remains fresh and relevant. The album, he writes, created “a consistent and emotional mood, with every one of the 12 tracks forming a whole. It was, in essence, a concept album about loss, alienation and the end of adolescence.

“Blending the true sound of Los Angeles – the full range of exotica, surf and lounge music – with the trademark Beach Boys harmonies, Wilson wrote a series of gorgeous, tricksy melodies and contrapuntal harmony parts that perfectly matched lyricist Tony Asher’s disquisitions on failure, loneliness and dashed dreams.”

It was probably David Wild who put it best. “Pet Sounds to me,” he has said, “is this beautiful marriage of a childlike innocence, emotional vulnerability and an adult sort of musical genius.”

Brian Wilson plays Pet Sounds at Kelvingrove Bandstand, Glasgow, on August 3