For almost three decades, Madlib has remained an elusive yet prolific figure in hip-hop. His reputation has been defined by collaborations, alter egos and the tireless creation of new music. So much new music.

There’s been music in tribute to the composer Weldon Irvine. Music remixing the catalog of Blue Note Records. Music inspired by India. Music inspired by film scores. Music for mainstream stars like Kanye West and Erykah Badu. Music for underground standouts like MF Doom and Freddie Gibbs. An untold trove of music in his personal archives that few other people, if any, have ever heard.

But until this week, the Southern California artist born Otis Jackson Jr. had never put out a traditional solo album. “Sound Ancestors,” due Friday, attempts to synthesize his vast influences and production approaches into a singular listening experience. And while Madlib had little interest in such a project (“I didn’t really think about it,” he said), someone else did, and helped bring it to life: Kieran Hebden, the British musician who records as Four Tet.

“I wasn’t looking at it being like I want to stamp my sound onto his in any way,” said Hebden, 43, who arranged, edited and mastered “Sound Ancestors” using hundreds of files that Madlib sent him over the past few years. “It was more, I want to take the things I like the most and make them as good as I possibly can.”

Madlib, 47, doesn’t do many interviews, and when he does, they’re rarely illuminating about his philosophy toward making music. He’s not standoffish or dismissive, it’s just clear that conversations are not where he wants to put his energy. When we spoke from his home in Los Angeles, it was on his wife’s cellphone. He got rid of his device years ago when too many people kept trying to reach him.

Raised in Oxnard, Calif., a city surrounded by strawberry farms located between Los Angeles and Santa Barbara, Madlib got his first smattering of production credits in the mid-1990s on tracks for the rap party animals Tha Alkaholiks. It wasn’t until 2000, when he put out the album “The Unseen” as Quasimoto, that he began to attract broader attention. Quasimoto had his own persona: He was a furry monster with a protruding snout, known for his unbound id and pitched-up voice.

“That was a little explosion in my peer group,” said Nigel Godrich, the producer known for his decades of work with Radiohead. “It was clearly somebody on the outside doing something really, really different and striking and really exciting.” Years later, after they all became friends, Godrich said he and Thom Yorke approached Madlib about rapping on one of the Radiohead singer’s solo albums. He politely declined.

Madlib’s next breakthrough came when he released back-to-back collaborations with two other rap cult heroes. On “Champion Sound” from 2003, he paired with the Detroit-born producer J Dilla to form Jaylib, swapping turns as they rapped over each other’s beats. And in 2004 he teamed up with hip-hop’s mischievous supervillain MF Doom for “Madvillainy,” long considered the enduring statement from two rap geniuses.

After Dilla’s death in 2006, Madlib decided to stop rapping. “I just didn’t have anything to say anymore,” he said. “I didn’t really like rapping in the first place. I did it because I had to at times.”

During the 2010s, he found a reliable partner in Freddie Gibbs, and co-produced “No More Parties in LA” with Kanye West in 2015, creating a nimble piece of sleazy funk that inspired a multitude of T-shirts and hashtags. Amid all these projects, Madlib periodically released instrumental collections, usually as part of his “Beat Konducta” series, featuring more than 30 tracks, each of which rarely lasted more than two minutes.

With “Sound Ancestors,” Hebden hoped to craft a Madlib album that brought together all those years of work, but was more accessible. He wanted to deliver an immersive journey akin to what the moody Scottish duo Boards of Canada might do, or something the adventurous German label ECM Records would have put out in the 1970s.

Though Madlib is oriented around hip-hop and Hebden centers his sound around electronic dance music, they cite many of the same kinds of older records as influences. They are both deep appreciators of English psychedelic rock, free jazz and other far more esoteric microgenres. “We all collect the same things,” Madlib said. “He’s a little more out there than me. He collects nature and bug sound records. I’m going to get there.”

When they first met, Hebden was already a fan of Madlib’s creations. “He’s able to take elements that other people can’t, and turn them into something so cool and so beautiful and so undeniable,” he said. “It sort of flows out of him.”

Madlib and Hebden’s connection goes back to 2001, when artists from the indie rap label Stones Throw came to D.J. in London and Hebden introduced himself to Eothen Alapatt, the label manager known as Egon, outside the venue. The two stayed in touch, developing a deep friendship over the years that Madlib quickly became a part of.

“He’s more like a brother,” Madlib said of Hebden now.

Hebden had always wanted to hear an instrumental Madlib album, and realized he’d have to shepherd it himself. Alapatt, who partnered with Madlib on a new label, Madlib Invazion, started sending along material that Hebden used to create a 15-minute proof of concept. In 2019, he got final approval from Madlib over a dinner of Mediterranean food in London.

Madlib has always been hesitant to let other people touch his tracks; Hebden was one of the few exceptions. In 2005, Stones Throw put out an EP filled with Four Tet remixes of songs from “Madvillainy” that featured entirely new beats Hebden constructed as a way to experiment using Doom’s a cappellas. For “Sound Ancestors,” Hebden decided that although he could alter and manipulate the material Madlib sent him, he wouldn’t create any new sounds.

Madlib and Alapatt delivered hundreds of files: unreleased or unfinished beats, as well as live instrumentation that Madlib recorded with musicians during studio sessions. “I wanted him to be free to do what he wanted,” Madlib said. “I trust him to do what he feels.”

When the pandemic came and all touring possibilities ended, Hebden settled into the home he has in the Catskill Mountains in New York to focus on completing the album. He sent skeleton versions to Madlib, who would tell him if there were certain bits he didn’t like or featured parts he was saving for another project.

Beyond his ability to find obscure loops, there’s an unpredictability to Madlib’s music that comes from his jarring beat shifts and strange sample flotsam. He never lets listeners settle too deeply into a groove, and Hebden made sure to preserve some of that chaos. “I was trying to get the best of both worlds in terms of it having these moments that are very universal that everyone can get their head around, and also having shocking moments,” Hebden said. “I didn’t want to water anything down or make it too polite.”

The first single, “Road of the Lonely Ones,” is a melancholy exploration mostly built off segments from a breakup song by the 1960s Philadelphia R&B group the Ethics. Aching with heartbreak, it transforms the group’s question to an ex-lover, “Where did I go wrong?” into something far more existential. “Two for 2 — for Dilla” is no less sentimental, even if the song structure is less traditional. Soulful fragments warp, ricochet and bleed through, evoking the sample masterworks of Madlib’s departed friend and collaborator.

“It’s very much in keeping with what you would hope it would be,” Godrich said of the album. “It’s a relief to hear it.”

Following “Sound Ancestors,” Madlib hopes to start releasing a new album every month through Madlib Invazion. He offhandedly mentioned collections he’s put together based around both calypso and industrial music, material he recorded with Brazilian artists and an indie rock album made with the jazz-funk weirdo Thundercat.

Then again, he’s had numerous rumored projects over the years never materialize, including a collaboration with Mac Miller, a Black Star reunion album and a sequel to “Madvillainy.” But why get caught up in the past when there’s always something new?