LaShonda Katrice Barnett had just finished a nice rooibos at a tea salon when she overheard some people at a nearby table.
“They were all on their mobile phones and someone said, ‘Stephen Sondheim passed away just now,’ and I screamed ‘Oh no!’ very loudly,” Ms. Barnett, 47, said. “I jumped up, went into the bathroom, cried a lot for a while. Threw up.”
She immediately knew her next move. “I thought, ‘I need to be with people in grief,’” she said. “So I came here two hours ago, and I’ve been here, singing and crying.”
“Here” was the Greenwich Village piano bar Marie’s Crisis Cafe, where a line formed in the late afternoon and never let up for hours as fans gathered to commune, aware that they would be surrounded by people who not only perfectly understood their feelings, but who also knew Sondheim deep cuts and could nail tongue-twisters like the “Bobby baby, Bobby bubi, Bobby” line from “You Could Drive a Person Crazy.”
“I had other plans tonight,” said Mark Valdez, 28. “My family’s busy for the Thanksgiving holiday, but then we found out that Mr. Sondheim died.” Asked if he had ditched them to go to Marie’s, he laughed and then choked up a little: “Oh no, I just brought them. It’s a family here and I want to be with family.”
Jim Merillat, 63, was at the piano from 5:30 p.m. until 10 p.m., playing Sondheim tunes the entire time. “This was a place to process the news and celebrate his life and his work,” he said, chatting with friends an hour after his shift had ended.
“I found that phrases or even fragments of phrases in songs would catch me in a different way because now it was about him,” he continued. “I found myself a little choked up several times through the evening.”
Across the street from Marie’s, the mood was decidedly more raucous at the Duplex, where an ad hoc reunion of “Mostly Sondheim,” an open mic that ended a 12-year run in 2016, was underway. Inside, musical-theater insider jokes freely mixed with raunchy profanity and references to “The Real Housewives of Salt Lake City.” The appreciative room fell into a hush at all the right moments, though, as when the music director Brian Nash teared up during the spoken opening of “Sunday in the Park With George.”
“See, I’m crying so hard, ” he said. Then he and hosts Emily McNamara and Marty Thomas went straight into the upbeat “Comedy Tonight.”
Shortly after hearing the day’s news, Mr. Nash decided to bring back “Mostly Sondheim.” Luckily, the upstairs cabaret at the Duplex, a few doors down from the Stonewall Inn, was available. “It seemed important to hold a space for folks to feel whatever they needed to, to sing and cry and laugh and be with people who understood what a loss this was to those who love theater,” he said in an email sent near dawn.
He had no problem rallying the troops.
“I was so ready to go home and go to bed,” said Ms. McNamara, who had been at a big family gathering in New Jersey. “But when Brian called me I was like, ‘I’ll chug some caffeine, put on some lashes, and let’s go!’ ”
There was trivia: “Now we’re going to find if there are actual nerds in the room: On what song did Sondheim write the lyrics under the pen name Esteban Río Nido?”(Answer: “The Boy From …” with music by Mary Rodgers.) And there were reminiscences about first encounters with Sondheim, and of high school performances.
And even those stuck at home could join in when Telly Leung (who was once in a Broadway revival of “Pacific Overtures”) encouraged the crowd to sing along to “Not a Day Goes By” — the event was livestreamed on Facebook. (A commenter rejoiced: “I am trapped in Delaware with no access to a piano bar. Thank you Brian and all for bringing the tribe to me.”)
Others mourned and celebrated Mr. Sondheim at the theater: he had shows running on Broadway and off when he died, and Friday night’s performances were exceptionally emotional.
At the Classic Stage Company, which is presenting “Assassins,” Daniel Jay Park was there to celebrate his 40th birthday, but also to honor a master, whom he had worked with when he appeared in the 2004 revival of his musical “Pacific Overtures.”
“Whenever any one of us would mess up, his head would just lift up from the newspaper and we would all know,” he recalled before the Friday evening performance. “Before any note was given, we would all know that something was wrong and we had to go back home and study, fix it.”
Eric Anderson Jr., 38, a voice teacher and music director who lives just outside of Boston, was visiting New York for the holiday when he saw the news about Mr. Sondheim. Almost immediately, he told his husband he needed to go for a walk.
He ended up gravitating toward Times Square — and decided on a whim to go on something of a pilgrimage to Mr. Sondheim, visiting the Broadway theater named after him and then the Bernard B. Jacobs Theater on 45th Street, where the new revival of “Company” was set to begin at 8 p.m.
He saw people standing in line hoping for a last-minute ticket, and decided to get one too.
“Our industry and our art form owes everything to him,” Mr. Anderson said. “I teach him to all of my students, of course. He is the history of American musical theater in one person.”
Matt Stevens and Sadiba Hasan contributed reporting.