Sgt. Pepper: It Was Fifty Years Ago Today. . .

The Beatles (clockwise from top left, Ringo Starr, George Harrison (1943 - 2001), John Lennon (1940 - 1980) and Paul McCartney) pose for a photocall to promote their album 'Sergeant Pepper's Lonely Hearts Club Band', May 22 1967. John Pratt/getty

In the summer of 1967, few other bands could have released Sgt. Pepper's Lonely Hearts Club Band. [The album is re-released in a special edition today May 26. Sgt Pepper was released in the US on June 1 1967.]

Aside from the argument that few groups could have written and recorded such an album, the fact is that most record companies would have never released such a collection had it not come from a top act.

First, there was no single on Sgt. Pepper. In many ways it was the complete album that mattered—the whole in this case was greater than a sum of its parts. But Beatles albums—in the UK at least—were frequently released without the hit singles, and the Beatles did release a separate single that same summer, "All You Need Is Love."

What would instead have caused a problem for the seasoned record exec is the broad stylistic range of Sgt. Pepper.

In the pop-music world before Pepper, it was considered crucial for any artist to have a distinctive signature sound. For singers, it was usually a combination of the quality of the voice, the manner of delivery, and the selection of material. For bands, the list might also include particular instrumental sounds and textures.

Listening to Sgt. Pepper tracks such as "She's Leaving Home," "A Little Help from My Friends," "Being for the Benefit of Mr. Kite" and "Within You Without You," however, does not give the sense of a single trademark sound. We hear those wildly contrasting tracks as Beatles songs now, but if we had never heard of the Beatles before, would they sound like they came from the same group?

Part of the power of the Beatles' influence arose from the fact that they routinely employed their great popularity and commercial success to gain a license to experiment and expand musically.

Since the release of Help! in 1965, the band had been trying new things. At first these innovations occurred in small ways, but as Rubber Soul (1965) and Revolver (1966) emerged, a touch of sitar on "Norwegian Wood" became the sitar-driven "Love You To."

The intimate strings of the mildly philosophical "Yesterday" became the spikey chamber strings and social alienation of "Eleanor Rigby." The wispy reminiscence of "In My Life" became the psychedelic reverie of "Strawberry Fields."

With Sgt. Pepper's Lonely Hearts Club Band , the Beatles cashed in their music-business capital to create their most ambitious and experimental project yet.

The album began around the theme of Lennon and McCartney reflecting on their childhood growing up in Liverpool. But when the label needed a single in early 1967, Paul's "Penny Lane" and John's "Strawberry Fields" were released as a double-sided single.

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McCartney then hit on the idea of creating a fictitious group, inspired in part by a trip to San Francisco and the practice of long and fanciful band names. The Beatles became Sgt. Pepper's Lonely Hearts Club Band, and the album art played along, resulting in the iconic cover photo.

The first two songs on the album follow the Sgt. Pepper idea, but then that idea breaks down. The remaining songs simply follow one another as they would on any other album, with a reprise of the title track just before "A Day in the Life."

The album was hailed as the first "concept album," though Lennon always objected to this, saying his songs had nothing to do with the Sgt. Pepper idea. But in some ways, it doesn't matter whether the album really was a full-fledged concept album. People believed it was a concept album and soon musicians started imitating what they thought it was.

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The elaborate album art and packaging, the printing of the lyrics on the cover, and the stylistically eclectic music designed more for listening than dancing—all these combined to elevate rock music to become something more serious-minded than "I Want To Hold Your Hand" and "She Loves You" had ever been.

This shift of focus to the album at the expense of the single—a movement that has Sgt. Pepper at the center—transformed rock music in the years after 1967. As the whole became more important than the parts, record company bosses were scrambling feverishly to find records that sounded like Sgt. Pepper. An album that might not otherwise have been released now became the new model within the rock music business.

Without the Beatles' willingness to use their success to underwrite their musical adventurousness, however, things in pop-music might have gone very differently. It was fifty years ago today when Sgt. Pepper taught the band to play.

John Covach is Director, University of Rochester Institute for Popular Music.