Sally Wilfert met Rebecca Luker almost 20 years ago, when both were cast in the reading of a new musical called “The Mistress Cycle.”

“I knew who she was, of course, but I had never met her,” Wilfert says of the Helena native and Broadway star of “Phantom of the Opera,” “The Sound of Music,” “The Music Man,” “Show Boat” and other shows.

“At one point, I said, ‘I have to go the bathroom,’ and she said, ‘I’ll go with you,’” Wilfert recalls with a laugh. “We sat next to each other in the stall, and that’s where it all began. That set the tone. We became fast friends.”

Luker, a three-time Tony Award nominee, died in December at 59 of complications from amyotrophic lateral sclerosis (ALS). Wilfert is one of the Broadway and theater luminaries appearing in “Becca,” an all-star streamed concert May 4 at 6:30 p.m. Presented by Target ALS, tickets for the show are $20, and proceeds will go to ALS research. In addition to Wilfert, those appearing include Kelli O’Hara, Kristin Chenoweth, Norm Lewis and Laura Benanti.

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Though Luker’s husband, “Moulin Rouge” star Danny Burstein, is not part of the concert, he was pleased to lend her name to the effort when asked.

“I know Becca would want to help find a cure for this illness and, in a way, she is,” he says. “And will.”

During the live stream, Wilfert will talk about “All the Girls,” a show and CD she created with and performed with Luker.

Sally Wilfert, left, and Rebecca Luker in their performance of “All the Girls” at Merkin Hall in 2019. (Photo courtesy of Sally Wilfert)

“All the Girls” would turn out to be Luker’s last project, but it began with a successful show in September 2019 at New York’s Merkin Hall. In it, Luker and Wilfert celebrated women (and their friendship) through songs by the likes of Lin-Manuel Miranda, Stephen Sondheim and Stephen Schwartz.

“We had done the show a year earlier as a cabaret show before we expanded it to the full-length version,” Wilfert says. “We had so much fun. Thank God we made an archival recording of it.”

That recording would prove to be fortuitous since a planned studio recording was derailed by COVID-19 and Luker’s illness. Instead, producers of the album were able to take vocals by Luker and Wilfert from the live show recording and mix those with new orchestrations.

Luker was involved most every step of the way. The CD was released digitally on Christmas Day, but Luker was able to hear the final product before she died Dec. 23.

“That was her final project,” Burstein says. “She was fiercely proud of it. … She worked on it almost until the day she passed. She listened to the tracks over and over, giving notes and striving to make it the best it could be. It was beautiful to see how focused she was on getting it right despite being so very ill. It gave her hope, it made her feel special. I weep to think I’ll never hear her sing another song. That stunning voice. That glorious gift. That gorgeous soul.”

Sally Wilfert sings in the “Becca” fundraiser. (Photo courtesy of Target ALS)

Wilfert, too, saw Luker determined to make “All the Girls” the best it could be.

“I think that time for her, she rose to the occasion, and it made her feel, in a time when this disease was accelerating, it helped her forget it was happening and made her feel like herself,” Wilfert says. “She was able to have all the input in the world, and she was right on her game, as sharp as could be. She loved every second of it. … She did hear the final product, and she loved it.”

For her part, Wilfert says she was “honored and blessed” to have Luker in her life.

“I’m really very lucky that she was not only my best friend, but my collaborator, and that we could share art together,” she says. “She supported me and believed in me. When you’re a woman in this business, it’s very rare you find other gals you can trust and be as supportive as we were of each other. We felt very, very lucky.”

Burstein says the past few months have been “awful at times.”

“We were inseparable for almost 24 years,” he says. “We hated to be away from one another, even for a day, so it’s been a tough, lonely transition. But slowly, I’m doing my best to move forward despite this new reality and focusing on being grateful for all the time we had together.”

He’s grateful for the Broadway community, many of whom pitched in to help Burstein and Luker during her illness.

They also are giving their time and talent for the “Becca” fundraiser.

“All these people are dear friends and colleagues,” Burstein says of the performers. “Becca cherished their friendship and love. I’m honored they said yes.”