Emerging from the Covid-19 pause, Boston-area Celtic fiddler Hanneke Cassel felt she had a lot of unfinished business – musical and personal.

Going into 2020, she’d had plans to work on a new album featuring tunes she’d written since her 2017 release, “Trip to Walden Pond,” a period during which she and husband Mike Block welcomed their daughter, Eilidh – an event that has, not surprisingly, provided inspiration for more compositions.

Those plans did not work out, although she did wind up recording two “unplanned” albums that were done remotely, “Over the Sea to Skye” (in which she revisited traditional Scottish and Cape Breton tunes from early in her fiddling career) and the Christmas-themed “O Come Emmanuel.”

But an unfulfilled album project was only part of what weighed on Cassel’s mind.

“I had three very close friends pass away in a short time,” she explains. “Their passing, mixed with the pandemic and all the different kinds of losses many of us went through – of missing family, community and celebration – was a lot to take. So, I started writing tunes as a way to process what I was feeling and experiencing.

“There was a time, earlier in my life – like in my 20s – when I might write some tunes that were kind of angsty, maybe because I was upset about a relationship, for instance. But this period from 2020 through 2021 in particular felt like a different kind of sadness, of loss. It’s not angsty, but more existential: There’s still a joy in what you’re doing, but it’s also complicated and hard to understand at times.”

The fruit of all these labors is Cassel’s newly released seventh album, “Infinite Brightness,” which she’ll be spotlighting at a May 12 concert as part of the Second Fridays Concerts series at First Church of Belmont (404 Concord Avenue); she’ll also be appearing on May 13 at the Cultural Center of Cape Cod in Yarmouth.

Don’t get the idea that “Infinite Brightness” is a moribund affair. As Cassel notes, some of its tracks contain tunes she wrote as commissions for weddings, anniversaries, birthdays, grandchildren “and love.” In other words, pretty much the full spectrum of human experience – and when it comes to expressing this musically, Cassel is as good as it gets. For more than two decades, she has infused her fiddle music – whether interpreting from Scottish, Cape Breton or other traditions, playing her own material, or covering other contemporary fiddle tunes – with a singular passion as well as technical brilliance, from soulful slow airs to boisterous strathspeys to exuberant reels.

Rather than a changing cast of guest stars as on some of her past albums, Cassel has a defined ensemble accompanying her on “Infinite Brightness,” with Jenna Moynihan on five-string fiddle, Tristan Clarridge on cello, and Keith Murphy – who co-produced the album with Cassel – on guitar and harmonium; Yann Falquet plays guitar on two tracks. “It’s the first time in a long while I’ve had a consistent band for a recording,” says Cassel.

The reel “Evacuation Day” is an appropriate opener for the album in a few ways. For one, Cassel wrote it on March 17, 2020 (“when we thought the world was ending”), as Covid truly began asserting itself – certainly in the Celtic music community with so many St. Patrick’s Day-related gigs gone, which proved to be the prelude to months of little to no work. (That said, Cassel notes that the tune title was prompted by her husband’s rather humorous unfamiliarity with the Suffolk County holiday.)

But there’s a stoicism and hopefulness to the tune, with Murphy’s trademark pulsating guitar setting tempo and rhythm at the outset before Cassel enters, moving quickly and effortlessly between high notes and low. Moynihan trades off between melody and harmony, and Clarridge’s entrance about halfway through brings a solid, bassy foundation. He and Cassel play variations on the tune, sometimes both at once, suggestive perhaps of chaos and uncertainty – but then everything aligns at the end with some gorgeous strokes. (The official “Evacuation Day” video, shot in the Burren Backroom, depicts Cassel and various friends and collaborators in an increasingly festive, and whimsical, celebration. Watch it at youtube.com/watch?v=2HiAjzzxOzk.)

 Compelling backstories lurk behind some of the other tracks. One begins with “Raise Your Glass,” in which Cassel evokes the classic, jaggedly enchanting Cape Breton strathspey. The three-part reel that follows, “DFC,” is Cassel’s tribute to fiddler Graham DeZarn, who along with Cassel was a member of Boston-based fiddle ensemble Childsplay, which gave its final performance in late 2019; DeZarn died in July of last year at the age of 38. “I didn’t want to write something slow and sad, but fiery,” she says. “It wasn’t just sadness I was feeling, it was anger: ‘How could this have happened?’ So, I ended up drawing from the overall vibe and experience of being in Childsplay all those years: I took a riff I’d written for a Childsplay arrangement and made a B part and then a C part.” 

Another track has a nostalgic dimension for Cassel, as she ventures into the Irish tradition for a go at “The Long Note” (a source of some contention in the Irish music community as to whether it’s “Jenny’s Welcome to Charlie” in disguise or a jig that’s been repurposed as a reel), which Cassel learned as a teenager from Athena Tergis. The interplay with Moynihan and Clarridge is particularly striking here – that fifth string on Moynihan’s fiddle makes for quite some versatility in her accompaniment. 

Then Cassel and company ease their way into “Wood’s No. 1” by Iain MacLeod, a founding member of the mighty “acid-croft” Scottish band Shooglenifty, and weave some fascinating riffs and rhythmic patterns around the melody – Clarridge at one point does a bluegrass-style solo that eventually forms the backdrop for a reprise of the tune by Cassel. 

“The whole set is really kind of a blast from my 1990s,” she laughs.

Cassel’s life has always had a prodigious spiritual aspect, which she has often expressed in her music – the album’s title is taken from a line in Thomas á Kempis’ “The Imitation of Christ.” “She closes out the album with an instrumental version of the Carl Boberg hymn “How Great Thou Art,” displaying her not-to-be-overlooked skills as a pianist, and segues into the gentle “Cali’s Jig,” written in remembrance of Cali McKasson Kovin, a much-loved mainstay of the American Scottish music community.

 Along with everything else that’s gone on, for Cassel, these past few years also have been a period for redefining her musical identity. “For the longest time, I wanted to be known as a ‘Scottish/Cape Breton fiddler,’” she explains. “But at the end of the day, I’m not actually Scottish, or from Cape Breton, so what do I want to embrace? Of course, Scottish and Cape Breton are my favorites, and I play in those styles a lot and incorporate them into writing my tunes. But I also like Texas-style fiddling, which is what I started out playing in my teens, and hung around with Americana and bluegrass musicians, so those influences are definitely there, too.

“I started feeling more excited about that ‘Scottish American’ style, which includes Scottish and Cape Breton – and Irish – but has a very American accent to it. I still love playing the traditional tunes, playing for a traditional Scottish country dance. Or sitting down like a Cape Breton pianist and playing a bunch of Buddy MacMaster tunes. It seems I really connect with my audience the most, though, when I’m doing a combination of things – not just the trad stuff. I used to spend a lot of time trying to sound as ‘traditional’ as I could, but now I’m totally okay about having a Texas-style vibe in my music, or that ‘chopping’ style which I started doing when I was 18 or 19 years old. 

“That’s all part of my style and, I guess, my heritage,” she says, flashing her characteristically radiant smile, “So I’m going to go with it.”

Ticket information and other details for Cassel’s May 12 and 13 concerts in Belmont and Yarmouth are available at her website, hannekecassel.com