How did the album become an art form instead of a pile of singles?

The album became an art form when musicians began to treat a whole record as one work, and when critics started to agree. In the early 1900s a disc held only about three minutes of music per side, so popular recordings were short. Columbia's long-playing record, introduced in 1948, held some 22 minutes per side, about 45 minutes in all. For years, though, albums mostly served to promote singles. From the mid-1960s to the early 21st century the album was the dominant format of recorded music, a period called the album era.

Two records are usually named as the turning point. Brian Wilson of the Beach Boys heard the Beatles' Rubber Soul and thought it unified and free of filler, which was unusual when albums mainly served to promote singles. He made Pet Sounds in 1966, with studio musicians largely replacing the band. It is credited with using the studio as a compositional tool and with raising recognition of albums as cohesive works. In the United States it got a lukewarm response and peaked at number 10.

Then the Beatles stopped touring in August 1966 and spent months in the studio, this time without an absolute deadline. The result, Sgt. Pepper, is regarded by musicologists as an early concept album, and its reception is described as achieving full cultural legitimisation for popular music. Was it the first concept album? The critic Tim Riley said the Mothers of Invention's Freak Out! has claims, but that Sgt. Pepper made the idea convincing to most ears.