For 37 years it has been the stuff of legend, the greatest unreleased album: a word-of-mouth, bootleg-tape fueled urban myth, food for countless books, articles and, later, Internet treatises.

Scheduled for release in January 1967, Smile was to have been the Beach Boys’ follow-up to their innovative #1 single “Good Vibrations.” Described as a pocket symphony, “Vibrations” joined together separately recorded segments. For Smile, band leader Brian Wilson set his sights higher, seeking to create “a teenage symphony to God.”

It’s difficult to imagine now, but for a brief period in the mid-’60s, the Beach Boys, or more accurately Wilson, who wrote, arranged and produced all the band’s recordings, were regarded as The Beatles’ biggest rivals artistically. On hearing The Beatles’ “Rubber Soul,” Wilson was inspired to record “Pet Sounds,” an album lavishly praised in Europe and cited by Paul McCartney as a major influence on The Beatles.

But “Pet Sounds,” far removed from the surf, sun, girls and cars fare that had been the band’s staple, flopped commercially in the United States, sowing doubts within the band. As lead singer Mike Love succinctly told Wilson, “don’t f— with the formula.”

The pressure building on Wilson came to a head when the band returned from a successful tour of Europe and heard the complex and fragmentary Smile backing tracks Wilson had spent months recording with lyricist Van Dyke Parks. Deeply hurt by the lack of faith from a band that included his two brothers and his cousin, Wilson suffered a mental breakdown that would last more than 20 years. Every painstakingly assembled track was shelved.

Over the years a few tracks from Smile appeared on Beach Boys albums. With these and bootleg tapes, Beach Boy devotees assembled homemade “Smiles,” but the fragments only hinted at what Wilson had envisaged.

For some hardcore Wilson fans, the news that Wilson and his backing band had re-recorded pop music’s most-fabled lost album was greeted with joy and then doubt. Smile had become the “Holy Grail” of the music industry, a synonym for perfection. How could any album live up to such expectations?

Incredibly, Smile does. From the opening choral harmonies of “Our Prayer” to the closing bars of “Good Vibrations,” Wilson fuses together disparate song fragments, vocal acrobatics and flights of whimsy to astounding effect. Throwing off the ball and chain of verse and chorus, Smile is, even today, unlike anything that has come before.

The album is divided into three movements. The first charts the colonization of America, taking the listener from Plymouth Rock westward. The second, with tracks such as “Child is the Father of the Man,” tackles childhood and innocence. Songs themed around the four elements close out the album.

But it is Wilson’s ability to translate feelings into music that enraptures the listener. On songs such as “Wonderful” and “Cabin Essence,” Wilson layers harmony and counterpoint on top of gorgeous octave-scaling melodies. The final coda of the elegiac ballad “Surf’s Up” may be possibly the most beautiful piece of pop music ever recorded.

As good as Smile is, there are still regrets. Wilson’s backing band performs ably, but, as a vocal unit, the Beach Boys circa 1967 were without peer. The absence of Carl Wilson’s plaintive falsetto is particularly felt. The new version of “Good Vibrations” could never hope to match the original that Wilson labored for six months to complete. Finally, digital recording lacks that warmth that 1960s recording technology seemed to throw over everything it touched.

But there is no denying Wilson his belated triumphs. That of a precocious 25-year-old who composed, produced and arranged such a groundbreaking piece of work and that of a 62-year-old who had the courage to resurrect the music that heralded his mental collapse.

Pop music has had 37 years to catch up with Brian Wilson. He’s still waiting.

Brian Wilson will perform Smile at the Tampa Bay Performing Arts Center tonight at 7:30. Ticket prices are $45.50-102.50.