In 1967, the Beatles enjoyed god-like status internationally. As far back as the release of the Beatles film "A Hard Day's Night" (1964), the mop-topped Englishmen had conquered the planet - or were "bigger than Jesus", as John Lennon put it in 1966. But instead of continuing on the safe path to success, in 1967 the band ventured into unchartered territory with the now-legendary album, "Sgt. Pepper's Lonely Hearts Club Band".

"We were always being told, 'You're gonna lose all your fans with this one,'" Paul McCartney recently told "Mojo" magazine. "And we'd say, 'Well, we'll lose some but we'll gain some.' We've gotta advance." 

Indeed, when "Sgt. Pepper's" was released on May 26, 1967, the experimental music, surreal lyrics and abstract album cover meant the Fab Four had taken their ninth record in a radical new direction.

Revolutionary cover art

The first major concept album with a consistent story-arc, "Sgt. Pepper's" was also the first album with printed lyrics. Experimentation was also evident on the cover itself, which shows the four band members of in bright, multi-colored clothes standing in front of a montage of famous celebrities - including the controversial occult magician Aleister Crowley.

McCartney explained the importance of the colourful costumes to "Rolling Stone" magazine: "I thought, 'Let's not be ourselves. Let's develop alter-egos so we don't have to project an image that we know. It would be much more free. What would really be interesting would be to actually take on the personas of this different band."

Pop artists Peter Blake and Jann Haworth charged 3000 pounds (roughly 3400 euros) - instead of the then-average 50 - for the cover art. Still, it didn't prompt the Beatles to turn up to the photo shoot with a clear head: "If you look closely, you'll see that two of us are high," Lennon once told "Rolling Stone". The abstract cover made number 15 in the Top Fifty Millennium Masterworks list published in the "Sunday Times."

Marshmallow cake and sitar 

"Sgt. Pepper's" forever linked the Beatles with illicit, intoxicating substances. Songs such as "Lucy In The Sky With Diamonds," with surreal lyrics describing jam skies and marshmallow cakes, triggered public fear that it would tempt young people to consume psychedelic drugs. The serene ballad "A Day In The Life" was banned by British broadcaster, the BBC, due to a belief it "could encourage a permissive attitude to drug-taking." The Beatles denied this, saying the song was partly about media sensationalism.

Inspired by Indian philosophy, drug consumption and experimental composers such as Karlheinz Stockhausen and John Cage, "Sgt. Pepper's" saw the band embark on some daring musical experiments. The song "Within You Without You" was typical, combining Indian instruments including sitar, hypnotic harmonies and orchestral sounds into an avant-garde sound collage.

"It was nothing anyone had heard before, at least in this context," said McCartney. "It was a risk, and we were aware of that."

Blueprint of the music revolution

Whether the album justifies the many superlatives it receives remains a relative question. In the midst of their commercial high, The Beatles didn't just cash in but broke with the expectations of fans and critics by creating a challenging work of sound art. The risk ultimately paid off.

Long hair, colorful clothes, joints and the Beatles - "Sgt. Pepper's" could be heard in almost every park in 1967. The album topped the UK album charts for 27 weeks. "I maintain that the Beatles weren't the leaders of the generation but the spokesmen," said McCartney. With "Sgt. Pepper's Lonely Hearts Club Band", the band expressed the vitality of a youth culture that was questioning prevailing values. It also created a historic blueprint for future musicians.