"I've got nothing," says the British songwriter/multi-instrumentalist at the mere mention of the 26-year-old singer's name. "There are no clues."

He's understandably circumspect about his involvement. Since 21 has sold more than 10 million copies in the United States alone, according to Nielsen Music -- netting Epworth four Grammys in the process -- Adele has kept a low profile, leaving only stray gossip (Phil Collins told Britain's Q that she approached him to collaborate but then stopped returning his calls) and the occasional report from Ryan Tedder (who co-penned 21's "Rumour Has It") to hint at what might be in store for her next album. Other rumored collaborators: U.K. producers Kid Harpoon (Florence & The Machine), James Ford (Simian Mobile Disco) and balladeer-to-the-stars Diane Warren.

But as Sony Music -- and conceivably the world -- awaits the follow-up to her Grammy-sweeping opus, Adele is far from the only project that has recently occupied Epworth's time. U2's Songs of Innocence, Coldplay's Ghost Stories, Paul McCartney's New and Lana Del Rey's Ultraviolence featured his production in 2014; their collective merits helped him earn his second Grammy nod for producer of the year, non-classical. He also produced a standout track on FKA Twigs' breakthrough LP1 and oversaw the debut from quirky electro-pop act Glass Animals, the first signing to his Universal joint venture, Wolf Tone.

"He has been this background figure in terms of creating music in my life ever since I was 13," says Glass Animals frontman-songwriter Dave Bayley. "I couldn't believe he wanted to work with us."

Perhaps most impressively, Epworth managed to accomplish all this while rarely stepping foot outside the United Kingdom. That's because he recently became the new owner of famed London studio The Church (previously home to Eurythmics and David Gray), which hosted its first post-renovation sessions for U2's Songs of Innocence in early 2014, with Del Rey ("Black Beauty"), Twigs ("Pendulum") and Lorde ("Yellow Flicker Beat") all swinging by to record tracks for their latest projects. This development has allowed him to be closer to his family (his two kids and wife Danielle, a makeup artist). "Working studio life 48 weeks a year and still having a family is a jungle," he says. "I try to work from home when I can."

Epworth has quietly become one of the most in-demand producers by literally not going Hollywood. "I love working in L.A., but it's maybe fortunate to be a fish in a slightly smaller pond here."

That Epworth is gaining more attention across the pond is no surprise. His extensive track record dates back more than 10 years to working on Mercury Prize-nominated albums for Bloc Party, Friendly Fires and Maximo Park. Where those records were a mix of brash, bratty post-punk and danceable soul, his later collaborations with Florence & The Machine and Adele put him in a more commercial realm, which took even Adele by surprise. "He's known for being very indie and I'm known for being very pop," the singer said in a promotional interview for 21. Yet Epworth "just brought the light out of me," she added. "There's notes in there I never knew I could hit."

His more recent work with Coldplay, Lorde and U2 brings an icy quality to their respective sounds, but otherwise there's little connecting them. That's because his duties vary among projects. "Some artists just want you to stay there and be the filter for everything they create, so that they don't have to think about it," he explains. "Some people want you to create from scratch, and some people want you to become a member of the band without any further questions."

In lieu of pop stars, Epworth recently produced the first album in 35 years from post-punk Brit band The Pop Group, due Feb. 23 in the United Kingdom. As for the rest of his 2015 playbook, Epworth's keeping that close to the vest, too. Beyond a full-length for Rosie Lowe -- an alt-R&B singer signed to Wolf Tone globally -- he's light on details about his latest projects. "There's a couple of new acts we're working with," he teases, "but I always like to surprise."

And that Adele album? "That will come when it's ready."