The holidays are a fraught time for any family, and for the Dahls, the fictional family in Leslye Headland's new play Cult of Love that just opened at Berkeley Rep, Christmas requires a lot of negotiations, and singing.

The Dahl family, comprised of dad Bill (Dan Hiatt), mom Ginny (Luisa Sermol), two adult sons and two adult daughters as well as their significant others, are a musical bunch. Dad and at least two of the kids play piano, mom plays the violin, there are multiple guitar players, and the living room is littered with percussion instruments for any impromptu carol or hymn that might arise. Maybe this only happens on Christmas Eve, but it seems as though this is just one of the modes in which his family has operated as a unit for many years, and maybe the only mode in which they are all pretty happy being together.

Cult of Love opens with the family singing the Joan Baez-popularized "Cherry-Tree Carol," an English ballad that dates to about the 16th Century or earlier. It contains the lyric "Joseph gather me some cherries, for I am with child," a line that gives Ginny the opportunity to celebrate daughter Diana's (Kerstin Anderson) visibly pregnant belly.

Rachel Dahl (Molly Bernard), the acerbic wife of the eldest son Mark (Lucas Near-Verbrugghe), can be seen scowling in an arm chair with her wine, reluctantly pulling some bells out from under her so she can chime in on her cue. Meanwhile daughter Evie (Virginia Kull), a successful chef in New York, is in the dining room with wife Pippa (Cass Buggé), joining in the chorus from afar. And a man we learn is Diana's Episcopal priest husband James (Christopher Lowell) looks like an enthusiastic member of the tribe, playing multiple instruments and singing himself.

The family is waiting for Johnny (Christopher Sears), the black sheep son who, we learn, has been to rehab and is always the last to arrive, before they can sit down for dinner — and everyone is hungry.

This sets the mood for a complicated play about complicated family dynamics, about dealing with old grievances and aging parents, and about pride in various forms — and how that impacts one's relationship to family.

Headland has written a seven-play cycle about the seven so-called deadly sins, and Cult of Love, first performed in 2018, is the seventh and final play in that cycle, centered on the sin of pride. Non-Christians and even many Christians probably get confused and tripped up by this sin more than any other, because aren't we supposed to feel pride, in our accomplishments and in our families, for instance?

Cult of Love is more about the kinds of pride that tend to separate children from their parents and siblings, and the pride that keeps older people trapped in patterns and avoiding hard truths. It's also about pride that isolates one from everyone else, and how that can break bonds that once seemed unbreakable.

The dynamism of this play, the many personalities and inter-relationships it ventures to explain and unravel in an hour and forty minutes, is electric at times, and the production is masterfully directed by Trip Cullman. There are moments of chaos, but the play itself never feels too chaotic. And while it runs into fraught topics like the conflict of religion and LGBTQ identity, addiction, and mental illness, Headland is anything but heavy-handed.

The singing chops on several cast members — particularly the four Dahl kids — are also truly impressive, and add a surprise layer of sweetness and harmony amid much bitterness.

On the subject of drugs and higher powers the play is especially moving, as the key outsider character enters in its second half — Loren (Vero Maynez), a woman we learn is being sponsored by Johnny in a 12-step program and came along to his family's Christmas for emotional support.

"Nothing is more powerful than drugs," Loren says, dismissing most notions of "higher powers" even though she's tried crafting several for herself, and even as erstwhile seminary student Mark tries to convince her otherwise. But as he preaches, she softens, hearing that his version of God is unlike the one she grew up knowing.

"That's a pretty good higher power," she says. "A God who's designed to love me."

Maynez and Bernard both give standout performances as witty and dry non-Dahls who are looking in on all these dynamics, and who have some emotional distance. And as Diana, Anderson does a terrific job of oscillating between intense passion, pride, joy, and instability.

The play's multiple, significant dramatic turns are mellowed by humor — and this is a very funny play, despite the subjects it takes on. But more than just humor, music is the mechanism that keeps the play afloat, as well as this fictional family. They barely talk about it, but it is obvious how much it means to everyone, obligatory or no. If there are happy memories, and happy, communal moments still to be had, they're going to involve singing, even if it is just an easy escape.

'Cult of Love' plays through March 3. Find tickets here.

Top image: (l to r) Cass Buggé (Pippa Ferguson), Kerstin Anderson (Diana Dahl Bennett), Virginia Kull (Evie Dahl, kneeling), Luisa Sermol (Virginia "Ginny" Dahl), and Lucas Near-Verbrugghe (Mark Dahl) in Leslye Headland's 'Cult of Love'. Photo by Kevin Berne/Berkeley Repertory Theatre