By Scott McLennan

Circles Around the Sun has established a distinctive niche within the expanding universe of “Grateful Dead as genre,” appealing to the core audience for Dead music without having to pull songs from the group’s songbook.

Circles Around the Sun: the late Neal Casal at left, bassist Dan Horne, drummer Mark Levy, and keyboard player Adam MacDougall.

At first, guitarist Neal Casal did not intend Circles Around the Sun to last any longer than it took to record the instrumental passages intended for the intermissions at the Grateful Dead’s “Fare Thee Well” concerts in 2015. But, thanks to fan prodding, Circles Around the Sun became a going concern. And Casal did not want the band to fold after he took his life in August. In fact, the guitarist left behind a note asking his bandmates to release the album they had completed before his death and to carry on as a band.

On March 13, the eponymous Circles Around the Sun album, containing Casal’s final recordings, will be released. Ahead of that date, CATS has launched a tour that brings the band to the Sinclair in Cambridge on March 2. Guitarist Scott Metzger from Joe Russo’s Almost Dead will be joining Circles Around the Sun for that show and a few others this spring.

No permanent replacement for Casal has been named. According to bassist Dan Horne, one may not ever be named; instead, CATS may carry on with Horne, keyboard player Adam MacDougall, drummer Mark Levy — all of whom Casal first enlisted to be part of the project —  along with  different players and perhaps even different instrumentation.

“Maybe we’ll add a trombone if we’re lucky,” Horne said.

But to honor Casal’s legacy, which is so much a part of the most recent work, it makes sense for CATS to work with guitarists who are compatible with their groove-heavy, improv-oriented style. Soulive’s Eric Krasno was the first to step into the role in October when CATS played its first shows after Casal’s death.

“We’re honoring Neal,” Horne said. “Honestly, it feels like he’s there with us on stage. He was the captain, but the ship is still sailing. We thought about canceling those shows in October. Then we went ahead and did them. There was a very intense reaction from the audience. It was pretty special.”

Audience reaction has been key to the existence of the band. Casal rounded up some like-minded Grateful Dead fans to record the so-called interludes played during the set beaks of the five shows that the surviving members of the Grateful Dead performed in the summer of 2015 to celebrate the band’s 50th anniversary. Casal and MacDougall — bandmates together in the Chris Robinson Brotherhood — and Horne and Levy   jointly wrote the music. They pulled motifs and themes from a number of different Grateful Dead songs and then blended them into original instrumental compositions, which were recorded live in one take. The compositions accompanied visuals created by filmmaker Justin Kreutzmann, son of Grateful Dead drummer Bill Kreutzmann.

People who heard the music at the shows or experienced it by way of the myriad pay-per-view events staged around the country wanted to know who made the set-break compositions and where could they get them.

That led to Circles Around the Sun becoming a full-fledged band. The members toured around the commitments they had to other groups and worked on another album of original instrumentals. The album Let It Wander came out in 2018 and, like the Interludes for the Dead album, it featured lengthy instrumental workouts, but this time without the direct Dead flourishes.

For the soon-to-be released album, Horne said the band tried to come up with shorter pieces, expressly designed to get people moving.

“When we were playing a lot of shows in the fall and summer (of 2018) we were seeing what crowds were reacting to and  how that fit into what we wanted to do in terms of having higher energy material that would keep the dance groove going,” Horne said.

The forthcoming album features a punched-up sound, evident from the get-go with its opening track, “Baby Man,” which lathers on exuberant key and guitar lines atop a bed of taut drumbeats and insistent bass thumps. A video made for the song combines ’70s roller disco with animated space travel visuals. Horne explains,“I just thought this was a good song to skate to, and the idea just started from there.”

Mark Levy, Dan Horne, and Adam MacDougall. Photo: Piper Ferguson.

CATS’s third album is stuffed with R&B influences, of both the old and new school varieties. But there are also plenty of openings for musical freak-outs, some that pop up unexpectedly, such as the anarchy that erupts during “Landline Memories.”

“That was cathartic, like a meditation on chaos,” Horne said. “We just let it fly off of the rails.”

Horne said the album’s songs will take on new forms when played live; the band intends to keep the music open-ended, even though it wanted the writing to be kept concise.

The record features fine work by Casal, whose feel for loping melodies and smooth, exploratory jams will be missed. Metzger will not try to duplicate Casal’s work, Horne said. He will use it as a starting point.

“We told him, ‘Do your thing.’ It fits. He’s not bending one way or another, and we really like his desire to explore,” Horne said of Metzger. “He likes pushing the boundaries, and that’s where he and Neal intersect as players.”

Circles Around the Sun has established a distinctive niche within the expanding universe of “Grateful Dead as genre,” appealing to the core audience for Dead music without having to pull songs from the group’s songbook.

“Grateful Dead is a collective starting point,” said Horne, who also performs in the band Grateful Shred. “It’s the band that everyone in the scene loves to celebrate. And their music has a certain energy. Their tunes start with that energy, and that’s where we start.”

Scott McLennan covered music for the Worcester Telegram & Gazette from 1993 to 2008. He then contributed music reviews and features to the Boston Globe, Providence Journal, Portland Press Herald, and WGBH, as well as to the Arts Fuse. He also operated the NE Metal blog to provide in-depth coverage of the region’s heavy metal scene.