Epic indie-rockers the National just descended upon upstate New York to write and record their next album at guitarist/producer Aaron Dessner’s new home studio—and will test that material in a sole Northeast headlining date at Mass MoCA on June 11. But that’s far from the only thing that Brooklyn expat Dessner has grown in his rural spot over the border from the Berkshires.

Dessner—whose production credits include Mumford & Sons, Sharon Van Etten and the Lone Bellow—just finished an album there with Irish singer Lisa Hannigan. “Lisa and I have a lot of close friends in common, sort of the natural story of these similar communities,” says Dessner, who’ll reveal new songs with Hannigan when their band plays Boston Calling on May 27. “It’s magical. Normally I don’t perform [beyond the National], really, with people who I’ve made records with or produced, but this is so much fun.”

The guitarist isn’t only setting the table for Sufjan Stevens and headliner Sia on Boston Calling’s opening night. He’s co-curated the three-day biannual festival at City Hall Plaza since its 2013 inception. “We’ve always tried to make it diverse in terms of genre,” Dessner says. “There’s not a scientific method. It’s a discussion and an issue of what have we done before and what can we do differently.”

Yet all of those exercises seem like preparation for the massive project that he’s finally ready to drop after four years: Day of the Dead. The Grateful Dead tribute, which Dessner produced and curated with his twin brother and fellow National guitarist Bryce, spans nearly six hours of music on 59 tracks recorded with more than 60 artists.

The cast ranges from Dessner’s production clients and Brooklyn indie-scene brethren to classical minimalist Terry Riley, jazz pianist Vijay Iyer, Senegal’s Orchestra Baobab and fellow 2016 Boston Calling acts Courtney Barnett, Unknown Mortal Orchestra and Charles Bradley, whose grimy psychedelic-funk slant on “Cumberland Blues” stands out. The Dead’s Bob Weir joins the National and Wilco on separate live tracks, while the Flaming Lips and an alliance of Cass McCombs and Almost Dead head Joe Russo swap divergent takes on “Dark Star.”

“It’s a weird cultural document of the influence of this music,” Dessner, 40, says of the May 20 release, which benefits the Red Hot Organization’s AIDS charities. “It’s the kind of record that you can listen to as a playlist.”

Growing up in Cincinnati, he and his brother tuned into the Dead early on. “It was the music that made us want to be in a band, especially the sort of avant-garde, experimental streak in it, that it was always different,” Dessner says. “We didn’t listen to the Dead exclusively, because very quickly we got into alternative music, but it stayed with us.” Several years before they formed the National in 1999, he and Bryce joined drummer Bryan Devendorf in his attic and jammed the Dead’s “Eyes of the World” for seven hours, Dessner recalls. “Fast forward 25 years later and we’re still playing together.”

For Day of the Dead, the National’s instrumentalists (rounded out by Bryan’s bassist brother Scott) anchored a house band that backed many of the artists in upstate New York church studios. One high point came in a 16-minute “Terrapin Station” suite—featuring Grizzly Bear’s Daniel Rossen and Christopher Bear, the Brooklyn Youth Chorus and New York quartet So Percussion—that swells with strings and skitters with marimbas in sections the Dead never played live.

Dessner calls that 1977 opus one of the Dead’s greatest studio achievements but adds that he sought to replace the “bright Carnival Cruise feeling” of its “Terrapin Flyer” section with something “much darker and more intense.”

After that elaborate “Terrapin Station” production, “We were like, ‘We could be done,’ ” Dessner says of Day of the Dead, which will see a live mini-staging with several of its artists at Eaux Claires, an Aug. 12-13 festival in Wisconsin that he co-curates with Bon Iver’s Justin Vernon, who paired with Bruce Hornsby on the album.

But the more he talks about the Dead songbook, Dessner grows wistful. “This record could easily be twice as long.”

Aaron Dessner and Lisa Hannigan play Boston Calling at City Hall Plaza on May 27.