Holly Twyford is taking on her first full-scale musical as Desiree Armfeldt in “A Little Night Music” at Signature Theatre. (Bill O'Leary/The Washington Post)

On a humid summer morning, Holly Twyford, an actress whose adventurousness is well known to Washington theatergoers, is tackling what is perhaps the most terrifying challenge of her career.

Harmony.

She’s proved her mettle with the words of ShakespeareAlbeePinterBeckett. And now, she’s got a maestro of a more tuneful proclivity in her ear: Stephen Sondheim. Seated at a piano in Signature Theatre’s rehearsal room, her sheet music perched on a stand, Twyford is concentrating at the moment on imprinting in memory the final notes sung by Desiree Armfeldt in “A Little Night Music’s” playful Act 1 duet, “You Must Meet My Wife.”

For an actress in middle age who until now has never been cast in a musical, becoming Desiree — a role that’s been played on Broadway by the likes of Glynis Johns, Bernadette Peters and Catherine Zeta-Jones — is a bit like taking it, career-wise, from the top. Before rehearsals began, one of her comments to director Eric Schaeffer was: “This is going to sound like a silly question, but what do I expect on the first day?”

“Well, you’ll sing,” Schaeffer replied.

And so, in this first week of rehearsals in late July, she is doing just that, alongside Bobby Smith, who plays Desiree’s elusive, erstwhile lover, Frederik Egerman. As they work through the last lyrics of the duet, the show’s music director, Jon Kalbfleisch, tries to help Twyford home in on her notes — a D-sharp, an F-sharp and a G — at the same time Smith sings a C, an A and a B. For the tricky harmony, Kalbfleisch offers the actress a variety of strategies. “You’ve got to get used to singing at odds with him,” he instructs. “When he sings his note, you sing your note louder.” Twyford fixes her gaze on the music stand as the rehearsal pianist, Jacob Kidder, plays the concluding bar, corresponding to the words “Yes I/You must,” again and again. Each time he does, her voice is a tad more relaxed and the blending with Smith a mite truer.


Holly Twyford (Desiree Armfeldt) and the ensemble of “A Little Night Music” at Signature Theatre. (Paul Tate DePoo III)

“Cut! Print!” Kalbfleisch declares, at last, encouragingly.

“Oh, would that we could!” Twyford responds, and the room laughs with her.

The leap Twyford is attempting as Desiree, the starring role in the 1973 Tony Award -winning musical that Sondheim and book writer Hugh Wheeler adapted from an Ingmar Bergman film comedy, “Smiles of a Summer Night,” is more than an intriguing experiment. It’s a jump over an imaginary fence that has long seemed to divide actors into two distinct career paths — musicals or straight plays. Exceptions to this relic of conventional casting do occur. Still, actors often talk about the habit of directors and theater companies to pigeonhole them as chiefly suited to one discipline, and not seriously consider them for the other.

Choosing an actor with no musical training carries a higher degree of risk, no doubt, especially for a company such as Signature, which has a national reputation as a kind of Sondheimian home court. But Twyford wasn’t an unknown quantity: A native Northern Virginian, she has a résumé in theater in these parts going back to 1993, and estimable range. Some of her recent roles include Martha in “Who’s Afraid of Virginia Woolf?” at Ford’s Theatre and Bottom in “A Midsummer Night’s Dream” at Folger Theatre, to name just a couple. She has sung a song or two in plays over the years, so there was a facility evident for carrying a tune. And although Desiree performs the better part of what may be Sondheim’s most beloved ballad of all time, “Send in the Clowns,” the role was not conceived for a singer. Johns famously spoke-sang a good portion of her lyrics, in the manner of Rex Harrison in “My Fair Lady” and Richard Burton in “Camelot.”

It was Schaeffer’s idea to approach Twyford, who already appeared at Signature in plays: Douglas Carter Beane’s comedy “The Little Dog Laughed” and Laura Eason’s romantic dramedy “Sex With Strangers.” In the gently farcical, intermingled love stories of “Night Music,” Desiree is a Swedish actress of a certain age with a daughter to support, a woman weary of the road and still carrying a torch for Frederik, a lawyer besotted by a much younger woman he has foolishly talked into marriage. Eager to find someone Washington-based, with an affinity for the kind of characters of psychological richness in which Sondheim specializes, he invited Twyford out to Matchbox on 14th Street NW to talk.

“I knew she would act the hell out of it,” says Schaeffer, who over drinks handed her a thin, brown envelope containing the offer.

“Come on! People don’t want to pay to hear me sing!’ ” Twyford recalls saying.

Schaeffer remembers her expressing her fears in more colorful terms. To which he replied: “That’s exactly why you should do this.”

“Sondheim always said he’d rather have actors who sing than singers who act,” notes Schaeffer, who, 15 years ago, curated the six-musical Sondheim Celebration at the Kennedy Center, and in 2011 directed a revival of the composer’s “Follies” on Broadway. “And the other thing I knew was, Holly was going to understand this character: She has a kid, she is an actor, she’s had to sacrifice. I thought, ‘She’s going to get this world.’ ”

Holly Twyford. (Bill O'Leary/The Washington Post)

The thing Schaeffer could not have known he had going for him was that “A Little Night Music” was the favorite show of Twyford’s mother, Suzanne. The album was on continuous play during her childhood and, as a result, Twyford knew every lyric. “In my head, I decided reasonably quickly,” the actress says of the job offer. Later, she reports, her mother said to Schaeffer, “I would have killed her if she hadn’t said yes!”

To bone up, she asked accomplished actress-singer Tracy Lynn Olivera — cast in the show as the long-suffering Charlotte, wife to the inveterate roue Carl-Magnus (Will Gartshore) — for vocal lessons before rehearsals began. And to begin the process of absorbing Desiree into her being, Twyford was told she had to swear off the album. “I’m not allowed to sing along with Glynis anymore,” she says in not entirely mock sorrow.

“This has to be Holly’s Desiree, not Glynis’s,” Kalbfleisch says. At the rehearsal piano, he explains, his method is one of diagnosis and treatment: discovering what will elicit from an actor who has not spent years honing a technique the most satisfying musicality. “What I try to do is sense where they are and what their comfort level is and what they need,” he adds. “What works for one person may not work for another. If you say, ‘Try this’ and they look at you like you’ve got holes in your head, then you have to come up with something else.”

With Twyford, he says, “she’s obviously in­cred­ibly talented and there’s a brilliant sense of humor that informs everything else. And she does sing. She just hasn’t done it in a musical.” So there are technical aspects that Kalbfleisch has to accustom her to. Harmony is one of those, as is learning to sing with an orchestra and adjust to the reality that an actor cannot always rely on the orchestrations to provide the melody line. Surmountable? He thinks so. “Everybody who comes in here is a professional,” the music director says. “We’re all in here to get it right.”

Twyford emerges from the rehearsal professing herself stimulated by the new skills she’s acquiring. On this morning she’s also been practicing her Holly-not-Glynis version of “Send in the Clowns,” and Schaeffer likes what he hears. “Holly was already singing notes that Glynis never did,” he says. 

The unexpected places a life in the theater takes you. Isn’t it rich?

Drolly, Twyford reflects on the highs and the lows of becoming someone else, in this case, someone else who has to hit a D-sharp, F-sharp and a G.

“In another week,” she says, laughing, “I’ll feel as if I’ve made the biggest mistake of my life.”

A Little Night Music, music and lyrics by Stephen Sondheim, book by Hugh Wheeler. Directed by Eric Schaeffer. $40-$108. Through Oct. 8 at Signature Theatre, 4200 Campbell Ave., Arlington. Visit sigtheatre.org or call 703-820-9771.