Last year, most carol singing in Britain was canceled because of the pandemic. This year, a group of roving singers was determined to carry on, despite the Omicron variant.LONDON — Last Thursday night, many people in Britain were worrying about the Omicron variant of the coronavirus, and whether the pandemic was about to disrupt Christmas plans for the second year in a row.The country had just broken a record for new daily cases of the virus and Prime Minister Boris Johnson had urged the public to “think carefully” before going to Christmas parties.But for three carol singers standing outside Leadbelly’s, a bar in south London, there was a more immediate problem: a lack of tenors.Zoë Bonner, 41, a soprano and co-organizer of a caroling pub crawl to raise money for a homeless charity, explained that a scarcity of male voices “was always” an issue for choirs and carol singers.Then Peter Coleman, 24, strode across the square in front of the bar toward the group. “Houston, we have a man!” he said, introducing himself.Within a few minutes, the four singers began belting out an intricately harmonized rendition of “Deck the Halls” into the London night. When they hit the chorus, a group of nearby drinkers pushed themselves out of their chairs to see what on earth was going on.In Britain, the tradition of caroling dates to at least Victorian times and is mentioned in Charles Dickens’s novels.Tom Jamieson for The New York TimesSince the coronavirus pandemic hit last year, live singing has been arguably the most demonized of cultural activities, after it was linked to several superspreader events. An infected singer, projecting their voice across a poorly ventilated space, can quickly spread virus particles.Last Christmas, caroling — when singers perform door to door, or pub to pub, a tradition that dates in Britain to at least Victorian times and is mentioned in Charles Dickens’s novels — stopped in much of Britain after government guidance for the holiday season said singers should consider canceling events, even outdoors. Many carol services in the country’s churches and cathedrals also came to a halt.This winter, it seemed attitudes had changed, at least among British lawmakers. On Dec. 8, when Boris Johnson announced that masks would become compulsory again in most indoor public spaces in England, in response to the Omicron variant, he said that singers were exempt. (A government spokesman later clarified that this didn’t mean people could sing while shopping and avoid wearing a mask in grocery stores.)At Thursday’s caroling pub crawl, Meg McClure, the event’s other organizer, said she realized that the event carried a risk — it felt a bit like “caroling on the edge.” But every singer had done a rapid antigen test before attending, she said, and the group had decided to perform outside if any of the pubs they visited were too busy.Also, she said, there was a chance the singers would only be caroling to a handful of people, since many Londoners were deciding to stay home. “I called all the pubs earlier to make sure we could come,” McClure said. “One actually said to me, ‘I’m not sure we’re going to have anyone in, love — but you’re welcome to visit.’”The evening felt a bit like “caroling on the edge,” one caroler said, although each singer had done a rapid antigen test before attending.Tom Jamieson for The New York TimesWhen the group arrived at its first stop — The Salt Quay, a gastro pub overlooking the River Thames — it looked like that prediction might come true. The vast space contained only 11 drinkers, including three young men watching soccer on their phones. The group sang three carols, peaking with an uproarious “O Come, All Ye Faithful,” to polite applause, but few donations.At the next pub, The Brunel, it seemed things might be even worse. When the carolers arrived, the quaint venue had only five customers, two of them visibly drunk. But as soon as the group started singing — now boosted by another male singer, who had arrived late — they grabbed their audience’s attention.One of the pub’s patron’s, George Parrin, 77, pantomimed a heart attack when the voices soared. “Listen to these harmonies!” he shouted to a friend. The friend shushed him back.Two women moved close to the singers and swayed to the music, and several passers-by walked in looking surprised but happy to see the group. Spare coins and bills were soon landing in red collection tins.Molly Thomson, 26, said she had originally planned to go to a concert by the rapper Little Simz, but had decided not to go, because she was worried about catching the virus. “So this is amazing,” she said. “It’s the next best thing.”Outside The Mayflower pub, the eight-strong carol group sang a raucous “We Wish You a Merry Christmas” and the haunting “Coventry Carol.”Tom Jamieson for The New York TimesFor the professional singers in the group, like Bonner, the last few weeks had been some of the busiest since the pandemic began. This month, she had performed in 12 carol services and concerts, and had a regular gig singing Christmas music while afternoon tea was served at an expensive London hotel. After a year of struggling to make a living, those jobs couldn’t have been more welcome, she said, though she feared new public health restrictions could soon make the work dry up again.After a couple of hours, the roving chorus reached the final pub: The Mayflower, named after the ship that in 1620 took Pilgrims to what is now the United States. The group was now eight members strong — including four men. They stood on the pub’s terrace, looking out onto the Thames, and sang a raucous “We Wish You a Merry Christmas” and the haunting “Coventry Carol.”When they came to “Silent Night,” one of the onlookers, Clare Phillips, 32, turned to a friend and said, “This was my grandmother’s favorite carol,” then pulled her close for a hug.Afterward, the carolers gave one final performance on the cobbled streets outside the pub. People came to the windows of nearby apartments to listen, and customers drinking outside grabbed their phones to record the performance. A few even dared to join in.Helen Birkenshaw, a digital producer in her 40s, was one of those rapt by the singing. “These people just appeared out of nowhere,” she said. “It was like a little Christmas magic.” More