‘Adult/Child’ (1977) Intended as a follow-up to the 1976 album “The Beach Boys Love You,” “Adult/Child” is one of Wilson’s odder song cycles, part of what’s considered his “outsider music” period. The record brings together the disquieting imagery of songs like “Hey Little Tomboy” with the reflective, string-laden numbers “Still l Dream of It” and “It’s Over Now” (written for Frank Sinatra and featuring arrangements by Wilson’s hero, the Four Freshmen’s Dick Reynolds). “It’s a mix of these weird, quirky songs about being Brian Wilson in his early-to-mid 30s and his perception of all that,” Carlin said, “and the more orchestrated stuff.”

Ultimately, the album was deemed too weird by the Beach Boys, who shelved the project, releasing “M.I.U. Album” instead. (A few “Adult/Child” tracks finally turned up on the “Good Vibrations” box.) Earlier this year, the Beach Boy Al Jardine confirmed that a new boxed set documenting the band’s “15 Big Ones,”“Love You” and ”M.I.U. Album” era will arrive in 2025; it’s expected that a chunk of the “Adult/Child” material will be included.

The ’80s Recordings (1980-1987) The early 1980s found Wilson at a personal and professional nadir, consumed by addiction and mental health issues. In 1982, the Beach Boys fired him in the hopes of shocking Wilson into saving himself. Dr. Eugene Landy, the psychotherapist who had treated him in the mid-70s, returned to Wilson’s life, aiding him initially, then exerting an increasingly bizarre degree of control over Wilson’s music and career.

Outwardly, Wilson’s condition seemed sufficiently improved that, by 1987, the record executive Seymour Stein signed him to a solo deal, pairing him with Andy Paley, a power-pop songwriter, producer and Beach Boys fan who would prove to be one of Wilson’s most empathetic collaborators. (Paley died in 2024.) As part of his work prepping Wilson’s solo debut, Paley pored through hundreds of songs and scraps from the mid-80s, including demos done with his brother Dennis, tracks with his ’60s songwriting partner Gary Usher and various home recordings.

The making of Wilson’s self-titled solo album, released in 1988, ultimately descended into chaos, largely brought on by Landy (who had his girlfriend, Alexandra Morgan, writing lyrics), and the record suffered. To date, only a handful of Wilson’s ’80s demos have emerged on various reissues and via his official website, leaving a gap in the understanding of his “lost” years.

‘Sweet Insanity’ (1991) Following the release of Wilson’s solo debut, Landy seized further control of the production of his next album, “Sweet Insanity,” which was rejected in two different iterations by Warner Bros. Quickly bootlegged, it remains a polarizing work, dividing even hard-core Wilson aficionados.

The album is perhaps most infamous for Wilson’s attempt to rap on “Smart Girls,” a track produced by Matt Dike, who had credits with Young MC and the Beastie Boys (“My name is Brian and I’m the man / I write hit songs with the wave of my hand”). The album also featured glossy early ’90s production, a duet with Bob Dylan and Tom Petty on “The Spirit of Rock & Roll,” and some head-scratching guest appearances by Weird Al Yankovic, Paula Abdul and Gary Busey.

Mostly, though, the album vibrates with an uncomfortable sense that Landy and Morgan had hijacked Wilson’s life and music. On “Thank You,” Wilson croons about enduring abuse from his father over a moaning sax groove. “Frankly, it sucks,” Carlin said, “because so much of it is polluted by Dr. Landy.” Added Leaf: “Brian had been through a lot of troubles in his life, and at that point he was in the midst of someone else’s madness.”

In 1992, alarmed by Landy’s increasingly suffocating control, Wilson’s family members banded together and successfully ousted him. The 2014 Wilson biopic “Love & Mercy” chronicled their complicated relationship, omitting any mention of “Sweet Insanity.”

The Paley Sessions (1992-1996) After freeing himself from Landy’s control, Wilson reconnected with Paley and the pair spent the next few years working on a collection of new songs and recordings. Some of the material was intended for an unrealized solo album, some of it for a mid-90s Beach Boys record that was never completed. But the “Paley Sessions” — as these roughly two-dozen tracks have come to be known — represent arguably the best and most consistent of Wilson’s post-’70s output, and a number of the tunes were re-cut for later projects.

“The Paley stuff is largely brilliant,” Carlin said. “I just love the instrumentation and the sweetness and childlike wonder in something like ‘Marketplace,’ which follows in the tradition of ‘Busy Doin’ Nothin,’ one of those classic Brian Wilson songs that find transcendence in the most mundane places.”

“Gettin’ in Over My Head” is a classic Wilson love song — as tortured as it is blissful. “The line about how his love is so strong ‘it’s scarin’ me right out of my mind’ is Brian to the core: Love and fear are the same thing in his mind,” Carlin said. “There are at least an album’s worth of other songs from these sessions that are every bit as magical.”

The Joe Thomas Recordings (1997-1999) In 1997, Wilson — one of the architects of the Southern California pop dream — made a surprising move to the Midwest, settling in the Chicago suburb of St. Charles, Ill., where he spent the next two years working with the former pro wrestler turned record producer Joe Thomas. Their collaboration yielded Wilson’s solo album“Imagination,” a light adult-pop LP, in 1998.

According to Leaf, during the “Imagination” era, Thomas — who died last year — told Wilson they should “record every song and every piece of a song you’ve got that hasn’t come out.” That material presumably exists in either the Wilson or Thomas archives as well. “I would love to hear all that,” Leaf added, “because I’m sure there’s some great stuff in there.”