Brian Wilson’s triumphs, both in the 1960s with the Beach Boys and his remarkable comeback in the 21st century, are chronicled in this summer’s musical biopic Love & Mercy starring John Cusack and Paul Dano. It is an odyssey that would be unimaginable had Wilson not been introduced to cannabis in December 1964 by his friend Loren Schwartz, an assistant at the William Morris talent agency in Los Angeles. Wilson later told radio station KXOJ in 1977, “I got into marijuana, and it opened some doors for me, and I got a little more committed to music than I had done before, more committed to the making of music for people on a spiritual level.”

Originally, the Beach Boys combined the vocal harmonies of the 1950s quartet the Four Freshman with Chuck Berry’s rock ‘n’ roll guitar and sang about surfing, hot rods and the drive-in. As the group leader, Wilson wrote the songs, often sang lead, played bass, produced the records and managed the group. After he started smoking, he decided that he was not going to tour anymore so he could focus on the music. The Beatles and the British Invasion had conquered the American pop charts, and Wilson was determined to keep pace with them. He also wanted to stay home with Marilyn Rovell, whom he had married on December 7. Wilson gave what would be his last live performance for 12 years in Houston on December 23. Session musician Glen Campbell took over for him on stage, replaced a few months later by Bruce Johnston.
The first sign that his new lifestyle was paying off came on March 8, 1965, with the release of the new Beach Boys album Today! On the second side, Wilson broke away from the band’s high school formula with minor-key, introspective ballads featuring the Boys’ trademark lush harmonies over a vast array of instruments played by renowned Los Angeles session musicians the Wrecking Crew. “In the Back of My Mind,” for example, boasted an English horn, three saxophones, organ, Wurlitzer, vibraphone, harmonica and autoharp.

His next effort, “California Girls,” recorded in April 1965, presaged the “modular” approach he would develop over the next two years, in which his songs became comprised of many more sections than the typical pop song’s verse and chorus. He wanted the track to have a prelude that was completely different from the rest of the song, and the Bach-inspired intro became the piece of music in which Wilson took the most pride.

As the year progressed, he continued to explore his melancholy side with compositions like “Girl Don’t Tell Me” and delved into increasingly complex arrangements with “Let Him Run Wild” and November’s rapturous single “The Little Girl I Once Knew,” in which the song comes to a complete stop a number of times, confusing many a DJ.

Wilson became even more determined to push the envelope in early December 1965 after listening to the Beatles’ Rubber Soul with his wife and friends while smoking a joint. He was impressed that each song on the album was great, with no filler.

“I suddenly realized that the recording industry was getting so free and intelligent,” he explained. “We could go into new things—string quartets, auto harps and instruments from another culture. I decided right then: I’m gonna try that, where a whole album becomes a gas. I’m gonna make the greatest rock ’n’ roll album ever made!”

Released in May 1966, Pet Sounds was anchored by three of the group’s most famous tracks: “God Only Knows” (Paul McCartney’s favorite song), the euphoric ode to living together, “Wouldn’t It Be Nice,” and the dazzling folk rock “Sloop John B.” The album also features the booming timpani drums of “I’m Waiting for the Day” and the hymn-like “You Still Believe In Me.” But the rest of the album grows increasingly pensive, building to the epic resignation of “I Just Wasn’t Made for These Times” and the desolation of  “Caroline No,” mourning the death of innocence and love. The song cycle closes with the sound of a train barreling by, then fading into the distance, with dogs barking after it, evoking the feeling of abandonment at a lonely crossroads.

With nary a beach bonfire or drag race in sight, Wilson’s compositions incorporated elements of jazz, classical and lounge/exotica. His painstaking arrangements on cutting-edge (for the day) eight-track technology melded the Boys’ polyphonic vocals with the Wrecking Crew playing everything from Theremins to clarinets, flutes and bicycle bells. Rock magazines Mojo and NME have ranked the album the greatest of all time; Rolling Stone rated it second only to the Beatles’ Sgt. Pepper’s Lonely Hearts Club Band–which was an attempt to equal Wilson’s magnum opus, according to the Beatles’ producer George Martin.

In 2011, Wilson told CBC Radio that “Marijuana helped me write Pet Sounds.” And as for the follow up, “Good Vibrations,” Wilson told Uncut Magazine, “I accredit it to marijuana. I smoked marijuana just before I wrote it.” Alternately joyful and ethereal, the October 1966 single hit number one on both sides of the Atlantic and became an anthem for the bourgeoning hippie movement. Encapsulating the innovations of Sounds in three minutes and 35 seconds, it was comprised of six sections recorded over 17 recording sessions. The band’s publicist labeled it a “pocket symphony.” Wilson resolved that he would build his entire next album out of small song pieces – “modules” – to fashion “a teenage symphony to God.”

Smile seemed poised to top Pet Sounds with singles like “Good Vibrations,” the mini-rock opera “Heroes and Villains” and the tour de force “Surf’s Up.” The latter song’s abstract lyrics (co-written by Van Dyke Parks) were intended to convey how the old, traditional empire was being washed away by the counterculture’s “tidal wave.” But the track came to represent Wilson’s high-water mark at the exact moment before exhaustion and mental illness took their toll, when he gave a gorgeously eerie solo performance of the song for a December 1966 CBS News Special called Inside Pop: The Rock Revolution.

Wilson toiled on the album for 10 months, but a perfect storm of obstacles derailed the project. Band mate Mike Love argued against the album’s avant-garde direction. The group was embroiled in a lawsuit with former label Capitol Records. Guitarist Carl Wilson was prosecuted for refusing to be drafted. Wilson recorded countless song pieces, most less than a minute, and attempting to organize them created a morass of technical problems. And he was now suffering from manic depression and schizoaffective disorder, which often manifested itself in auditory hallucinations. On May 19, the Smile sessions were cancelled.

In September 1967, the band released Smiley Smile, which included lo-fi new songs and a few simplified re-recordings of Smile tracks. Fans had anxiously waited to see how Wilson would respond to Sgt. Pepper, and the LP was perceived as a failure.

Wilson was haunted by the Smile experience for decades, but gradually began playing elements of it in concert. In 2003, he reunited with lyricist Parks to finish the album, and performed it live in its entirety at the Royal Festival Hall in 2003. In 2004, he recorded a new studio version, the Grammy Award-winning Brian Wilson Presents Smile. In 2011, the original tracks from 1966-67 were reconstructed into The Smile Sessions, released to universal acclaim. Like his other masterpieces of the mid-’60s, the collection wouldn’t exist had Brian not taken his first toke at the end of ’64, back when the group’s current single “Dance, Dance, Dance” celebrated going to the sock hop.

Andrew Grant Jackson is the author of 1965: The Most Revolutionary Year in Music, Still the Greatest: The Essential Songs of the Beatles’ Solo Careers and Where’s Ringo?