WHAT BEGAN as a lark has gotten serious.

"When I first started, it was just something that seemed completely random," says Ruban Nielson, Unknown Mortal Orchestra's frontman and auteur. "I was just kind of like, 'Well, I'll just try it out.'"

That was 2010. After nearly a decade playing with his brother in the Mint Chicks, a punky garage group that achieved mainstream fame in their native New Zealand, Nielson settled in the Portland area. He had a kid, a job, and no intention of continuing to pursue music professionally. Ostensibly, he had quit. And he was fine with it.

Still, he tinkered with tape machines in his spare time, stitching together brightly coiled guitar riffs over crispy breakbeats and his own airy, wry falsetto. It was the music Nielson wanted to hear. He put a few songs online anonymously—hence the name—and they immediately caught fire. Records and world tours quickly followed.

"I made two albums just treating it like, 'I can't believe somebody wants to put my album out,'" Nielson says. "And now I've gotten to the point where I can't really do that anymore. I kind of had to face up to the fact that it's a real band, you know? It'd be kind of silly to keep acting like, 'Wow, little old me?'"

UMO's third record, Multi-Love, mirrors that sentiment. Playfully warped, upbeat, and funky, it is by many orders of magnitude a denser, richer, and more cerebral record than the first two.

"I felt like I was chasing something from the beginning," Nielson says. He decamped to his basement studio, recording at night and sleeping deep into the day. "I was really adamant that I wanted to make a record that felt like this moment rather than a lost gem, which is what those previous two albums were about," he says. His vision encompassed both substance and sound.

"I just wanted it to be this powerful, kind of vibrant record that was drawing on more of the '70s than the '60s," he says. As such, Multi-Love employs myriad synthesizers, and bits of R&B, funk, and disco snap alongside the pressing breakbeats. Then there are the words.