The cast of “Hairspray” at the Signature Theatre’s 25th anniversary concert. (Teresa Wood)

Notes from Signature Theatre’s cast-of-thousands 25th anniversary concert Monday night, an event that featured 70 artists, a full orchestra, flashbacks from favorite musicals, and knockout performances in waves:

Starting fast and brassy: Signature co-founder Donna Migliaccio opened with a brisk, easygoing “The Worst Pies in London” from “Sweeney Todd,” followed by Sherri L. Edelen ringing through Mama Rose’s “Some People” (from “Gypsy”) in sterling, rousing fashion. The roars began early.

Most riveting turns: The slow, forceful burn of Natascia Diaz, standing stock still (and in the shortest black dress of the night) through “The Flick Knife Song” from the recent “Threepenny Opera.” Also, Diana Huey, back from last year’s “Miss Saigon,” nailing every inch of the anguished “I’d Give My Life for You.”

Most ebullient performances: Megan Lawrence, a Signature star from the early days in the garage space that the troupe outgrew in 2007, and Carolyn Cole, sharing the anxious “Another Hundred People” from “Company.” Lawrence played Marta in 1993, and Cole played the role last year. More: Edelen and Nova Y. Payton, a pair of amiable powerhouses, always have fun together, and their honky-tonk cruise through the “Best Little Whorehouse in Texas” number “No Lies” was sheer joy.

Best 11 o’clock number: There were three, and pick ’em. Lawrence, in a tight spotlight, filled the vampy, lonely “Maybe This Time” from “Cabaret” with all the slow-blooming yearning you could want. Florence Lacey drew cheers in the middle of “As if We Never Said Goodbye” from “Sunset Boulevard” as her bright, high voice surged with the dark varnished tones of the orchestra — the once-glorious Norma Desmond, ready for her close-up.

And then, oh my, Payton. The remarkable thing about the electric, limber-voiced Payton is that she never showboats, even while wringing every last ounce of emotion from the gutbucket spectacle “And I Am Telling You” from “Dreamgirls.” When it was over, you had to check to be sure the walls hadn’t come crumbling down.

Sap and bombast: The concert, two acts and 27 numbers long, had overblown and maudlin moments. They were fleeting. Rightly, no one cared.

Casting: Huey reminded the audience why she was so ideal in “Saigon” (as was her co-star last year, Thom Sesma, though he wasn’t on hand Monday night). Rick Hammerly was a memorably terrific Hedwig in “Hedwig and the Angry Inch,” and he was back (in mesh shirt and Frankenstein boots) to soulfully croon “Wicked Little Town.”

New musicals: Stephen Gregory Smith and Bayla Whitten beautifully captured the weird uptempo sadness of “I Like (The Secret Song)” from Adam Gwon’s “The Boy Detective Fails,” which the company premiered in 2011. Nick Blaemire and James Gardiner fronted a group of students from Signature’s “Overtures” program in the uplifting, driving “My Next Story” from their 2008 “Glory Days.”

Old musicals: You wonder if Signature might stretch by risking this a little more often. “Threepenny Opera” was a very good stab earlier this year, and Tracy Lynn Olivera’s lightly melancholic way with “The Gentleman Is a Dope” from “Allegro” — like Bobby Smith’s jubilant vaudeville romp in “Everybody Loves a Scandal” — offered glimpses into the American musical’s nuanced and showbizzy roots. Signature generally pursues the latest edge — a virtue, for sure — but the company might expand its skills and vocabulary even further by reaching back.

Stephen Sondheim: Signature built its reputation on Sondheim but barely needed him Monday night. Stay tuned, though: The company will present an original Sondheim revue in the spring.

Continuity: The evening flowed easily and elegantly, overseen by the longtime brain trust. Artistic director Eric Schaeffer co-directed with relative newcomer Matthew Gardiner (the company’s young associate artistic director). Karma Camp choreographed. Jon Kalbfleisch conducted the orchestra. They and the artists who flooded the stage at the curtain call earned their champagne.