In a normal year, Phil Hines takes a deep breath, lays his hands on the keys of the 135-year-old pipe organ and begins to play.

The first notes of “O Come, All Ye Faithful” ring forth from some of the organ’s 2,200-plus pipes, creating a soaring herald that welcomes worshipers to St. James Catholic Church in Louisville, Ky., on Christmas Eve.

For the church’s music season this is the liturgical Super Bowl, an event planned months and months in advance. The voices of 36 choristers mix with the organ, a trumpet, a baritone horn, a violin, cymbals and the thundering timpani, as 400 congregants, packed cheek by jowl, join in.

Some arrive an hour early to get a seat.

This December, at St. James and churches around the country where the joy of Christmas is channeled through music, the celebration is, of course, different.

Given the coronavirus pandemic that has killed more than 300,000 people in the country, all that Mr. Hines, the church’s 63-year-old music director, can think about is how dangerous the night he looks forward to all year has become.

A soprano’s solo may now carry not just glad tidings.

The coughs of parishioners that once merely punctuated the music could be a public health hazard.

But there was no way Mr. Hines, who has weathered a soloist with laryngitis and an ice storm that stranded choristers, was calling off Christmas.

“I’ll bring the message of Christ’s birth to people however I can,” he said.

So this year, Mr. Hines has fashioned his “quarantine quartets” — groups of four who will sing at St. James’s Christmas Eve and Day services, accompanied by a violinist and percussionist, masked and socially distanced in the choir loft above the sanctuary.

His flutist and his trumpeter of 32 years, a former principal in the Louisville Orchestra, will watch from home.

“And I don’t blame them,” Mr. Hines said. “But it meant I had to put on my thinking cap.”

This is the mission music directors across the country are facing this Christmas. If the normal year presents the challenge of deciding between “Joy to the World” and the Hallelujah chorus, this season the question is how to celebrate the birth of Christ without creating a potential superspreader event.

Some churches, like Trinity Church Wall Street in Manhattan, are downsizing choirs and orchestras that might number more than 80 members to single-digit choristers for services they are streaming without congregations. St. John United Methodist Church in Augusta, Ga., recorded 85 current and former choir members singing the John Rutter carol “What Sweeter Music” individually, as well as three violinists and a cellist playing inside their homes, to create a video that will be shown during a prerecorded service on Christmas Eve.

Middle Collegiate Church in New York’s East Village, whose sanctuary was destroyed in a fire this month, recorded a video that now includes footage of a dancer both twirling around the sanctuary 16 hours before the fire — possibly the last person inside before it burned — and dancing outside the structure’s blackened skeleton. “It will make you weep every tear,” the Rev. Jacqui Lewis, the church’s senior minister, said. The church will also be streaming its 2018 CBS Christmas special on Christmas Eve.

But the Rev. Gary Padgett, the pastor of St. James in Louisville, said that even with all the prerecorded concerts and worship services available, it was important to the church to film its own music in house. “I always felt like if a member could see their own building, and their pastor, and the people they know performing music they’re used to hearing, it helps recapture some of the tradition,” he said.

Mr. Hines said he hoped that those who do turn up — whether it is 100, 50 or 10 scattered throughout a space limited to 125 people — connect with the simplicity. “It’s a different sound,” he said. “But if people watching still feel like they celebrated the birth of our Lord, and that the music helped them do it, that, to me, that will be a success.”

Father Padgett said that Mr. Hines’s encyclopedic knowledge of liturgical selections is unsurpassed, but that more than that, he is resourceful. When his soloist got laryngitis, Mr. Hines figured out a way for her to sing — by transposing the work down three semitones. (“Imagine a cross between Beverly Sills and Bob Dylan or Tom Waits,” he said.) For this year’s service, he rewrote bass and tenor parts for altos and sopranos so it would work with the choristers who agreed to sing. He outfitted his choir with special singers’ masks from nearby Bellarmine University. He will rely on the pipe organ to fill in the missing instrumental parts.

“It’s like the Whos are all gathered around, and the Grinch is looking down and he can’t figure out why they’re still singing,” he said. “Of course, they could hold hands, and we can’t do that. But we can still sing, even through a mask.”

Not everyone who is part of the tradition can make it. Jerry Amend, 75, the recently retired principal trumpet in the Louisville Orchestra would normally play five Christmas services in a 24-hour stretch. This, he said, will be the first Christmas he has spent at home since 1962. His mother-in-law is in a nursing home, and two people in her unit have died from the coronavirus. “I love performing, but it just seemed dicey this year,” he said.

Mr. Hines has cut his all-volunteer choir to 14 this year — fewer than half of his normal 36 members, but outsize in spirit, he notes. They have been rehearsing weekly, four or five at a time, since the second week of November, spaced out across the choir loft with individual music stands.

Joe Sullivan, 56, said the church had been his second family while teleworking as a meteorologist for the National Weather Service for the past nine months. The weekly rehearsals have helped him stay connected at a time when in-person interactions are rare. “It’s one of the few things that maintains a sense of normalcy for me,” he said.

Martina Gregory, 63, said the passion of the music director everyone in the congregation called “Pip” was infectious. Her daughter works in the emergency room at University of Louisville Hospital and has witnessed the pandemic’s toll firsthand, but Ms. Gregory is confident that the precautions — everyone present will be masked and pews will be disinfected after each Mass — will keep her safe.

“We’re singing, by golly,” she said. “I just hope we don’t have to do this again for Easter.”