The singers were unseen, filling the grand darkened space of Paris’s Saint-Eustache Church with song, like disembodied angels. They moved slowly in procession, up the aisles to a makeshift stage, where they revealed themselves: the men, women and children of the Notre-Dame Cathedral choir.

It has been more than two-and-a-half years since fire tore through Notre-Dame, the most visited church in the world and France’s most visited monument. The herculean task of restoring the medieval masterpiece was then delayed by the pandemic, but the French president has promised that the cathedral will reopen in time for the 2024 Paris Olympics.

The musical tradition at Notre-Dame is as old as the cathedral itself, with origins dating back to the 12th century.

But since the fire, the cathedral’s ancient music school and its choirs, called the Maîtrise of Notre-Dame, has struggled financially: the state and the city of Paris eliminated funding; the school lost one third of its 2-million-euros-a-year budget and had to fire most of its staff and musicians.

“We went through a period of deep mourning, but now we are motivated by the certainty that Notre-Dame will one day reopen,” said Yves Castagnet, the master organist who has played at Notre-Dame for 33 years. “Meanwhile, our mission is to preserve and spread the spirit of our great cathedral outside its walls. We have become the city’s ambassadors of sound.”

The musicians now perform like a band of musical nomads, awaiting their return home. Tourists — whether believers or not — who had made the Cathedral a pilgrimage site have been left bereft. The sense of loss is especially acute during the Christmas holidays, when Notre-Dame’s midnight Christmas mass doubled as a glorious organ and choir concert. But there is a surefire way to emulate the joy and comfort previously found at Notre Dame: Follow the music.

The cathedral’s closure has opened many visitors to a world overlooked even by Parisians themselves: the city’s more than 100 churches. Most of these have some music accompanying mass and Vespers; some attract master organists and choirs, who perform both scheduled and impromptu concerts — especially at Christmastime. Every church has at least one Christmas mass, but even churches that don’t regularly host concerts are likely to offer liturgical music at the end of December.

The cultural scene in Paris came back to life this fall, but now the uncertainty of the Omicron variant has cast a long shadow over the city. Currently, entry into all indoor spaces requires the presentation of a “pass sanitaire” (proof of vaccination, or a negative P.C.R. or antigen test no more than three days old). Masks must be worn indoors. On Dec. 6, the C.D.C. issued a Level 4 “do not travel” notice for France, indicating a very high level of Covid-19 in the country. The French government has decided to keep most public spaces, including restaurants, bars, museums — and churches — open over the holidays, but it is advisable to verify whether an event has been canceled.

Many of Paris’ churches have musically extraordinary organs (and organists) even if they do not also have a choir. Nearly 20 churches scattered across the city have organs made by Aristide Cavaillé-Coll, a 19th-century master organ maker, whose innovations ushered in a new era of organ construction and sound. Notre-Dame’s own Cavaillé-Coll organ has been under repair since the fire.

From musical mass and Vespers to open-door visiting hours, churches are free and open to the public — though best practice is to bring a two-euro coin to drop in a donation box. Concerts that are hosted rather than organized by churches will charge for tickets and they are best booked in advance.

Here’s where to find the musical spirit of Notre-Dame this holiday season.

Five Paris churches are playing host to the Maîtrise while Notre-Dame is under reconstruction. One of Paris’s oldest churches, St.-Germain-l’Auxerrois is a 15-minute walk along the Right Bank of the Seine and across the street from the Louvre. The cathedral’s religious services have moved there for the duration, along with some of its music.

Rebuilt many times over the centuries, the church is the resting place for many of France’s poets, architects, painters and sculptors. It is a visual adventure that blends several styles: a Romanesque bell tower, a High Gothic chancel, a Flamboyant nave, a Renaissance portal and a Flemish altarpiece and triptych carved in wood.

Vierge du Pilier, the most important statue of Mary to which people came to pray at Notre-Dame, is on display here. One of Paris’s most beautiful church organs is here — a 32-stop masterpiece built in 1771 by François-Henri Clicquot. It is undergoing restoration, but may be ready for Christmas. For now, Mr. Castagnet plays on a modern auxiliary organ installed near the main altar.

“Our repertoire is alive — we perform music that dates back 800 years and contemporary pieces that look to the future, Gregorian chants and Requiems and classic French Baroque and German romantic music,” said Henri Chalet, director of the Maîtrise de Notre-Dame.

Accompanied by the Maîtrise, the 5:45 p.m. Monday through Saturday Vespers and the 6:30 p.m. Sunday mass are broadcast on Catholic television’s YouTube channel. On Sundays, the 6:30 p.m. mass and the 10 a.m. Gregorian mass are broadcast on Notre-Dame Radio. (The Maîtrise also has recorded a Christmas album, À la venue de Noël, which can be heard on Spotify.) On Christmas Day, the Maîtrise is expected to perform during the 11:30 a.m. mass, as well as the 10 a.m. Gregorian mass. Plans for the usual Christmas Eve performance are uncertain because of Covid-19 considerations.

But St.-Germain-l’Auxerrois is too small to host to concerts with the Maîtrise’s large choirs, which have struggled to find other Paris churches willing to host them. About twice a month, they perform in other venues, especially at two of Paris’ best-known churches, both of them about a mile away: St.-Eustache near the Forum des Halles on the Right Bank, and St.-Sulpice (bigger than Notre-Dame), in the Saint-Germain-des-Prés neighborhood on the Left. St.-Sulpice plans to host a Christmas concert on the 14th.

St.-Eustache is considered a jewel of the French Renaissance, but it also can be seen as a mini-Notre-Dame. Its interior — including its perpendicular nave and transept and side and radial chapels — was modeled on the great Gothic cathedral. With its extraordinary acoustics, St.-Eustache regularly hosts concerts — from psalms to contemporary compositions. Even the ordinary singing of parishioners during weekend services stirs the soul. The 11 a.m. Sunday mass features both the church chorus and the organist, Thomas Ospital; there is also an organ concert at 5 p.m. on Sundays.

The church, host to other groups besides the Maîtrise, will be the venue for two planned classical music concerts at the end of the year, one on New Year’s Eve, and the other on Jan. 1, 2022.

St.-Sulpice is a late baroque building, constructed over the 13th-century foundations of a Romanesque church. If you want a 19th-century Eugène Delacroix fix, this is the place to go: two of his paintings and a ceiling fresco (magnificently restored) grace this venue. And it is just as famous for its renowned organ.

The St.-Sulpice 6,600-pipe organ, built by Cavaillé-Coll, is considered one of the most fabulous instruments in Paris. The brilliance of its construction is matched by St.-Sulpice’s excellent acoustics.

The church’s master organist, Daniel Roth, has a cult following. On most Sundays, he begins playing 15 minutes before the 11 a.m. Mass, then continues afterward with a well-loved 30-minute concert — blending styles and attracting organ groupies from around the world. Organ and choir music can be heard regularly here.

In addition to masses at regular hours, an 11 p.m. mass on Christmas Eve, a Christmas concert on Dec. 23 (from 15 to 30 euros, or about $17 to $34 based on current exchange rates), and a New Year’s Eve concert on the 31st (from 44 to 66 euros) are planned.

The Notre-Dame choirs are also performing at Saint-Étienne-du-Mont, a gothic structure in the Latin Quarter at the top of a gentle hill honoring Geneviève, Paris’s patron saint. Her mystical piety, fasting and shrewd negotiating skills are said to have stopped Attila the Hun from invading Paris in the 5th century. (Her ancient sarcophagus is housed inside.)

St.-Étienne-du-Mont is most famous for Paris’s only “rood screen,” an intricately carved, lofted-arch, 16th-century partition that serves as a decorative barrier between the high altar and the congregation.

Then there is its 17th-century organ, considered one of the finest in Paris, updated by Cavaillé-Coll in 1863, and restored several years ago.

This Christmas, the church has organized a play recounting the story of Saint Geneviève’s life (scheduled to run until Dec. 12; reservations necessary). Although no concerts are scheduled here for Christmas, the church’s organists will play at holiday masses.

Finally, the Notre-Dame choirs can be heard from time to time at Saint-Séverin in the Latin Quarter — not far from the cathedral and the Shakespeare and Company bookstore. Saint-Séverin was built in the late Gothic style in the 11th century; like Notre Dame, its exterior features gargoyles and flying buttresses; there is a rose window above the west entrance. The Maîtrise will be at St.-Sulpice and St.-Germain-l’Auxerrois this Christmas. Saint-Séverin plans to offer two classical concerts: the predominantly-string orchestra Les Solistes Français on Christmas Day, and a trumpet and organ recital on New Year’s Day.

Paris has more Cavaillé-Coll church organs than any other city in the world — and many of these are not far from Notre-Dame. The Sainte-Clotilde Basilica, on the Left Bank near Les Invalides, is a beautiful space to go in and pray, and there is a concert on the 1859 Great Organ every second Saturday of the month (except in August) at 5 p.m. The Basilica’s choir also practices on Saturdays from 5 to 6 p.m. in the Las Cases room, and on Sundays starting at 10 a.m., before its participation in the 11 a.m. mass. On Dec. 11, the Choir of Paris, a group of about 60 professional and amateur singers, is scheduled to perform Handel’s Messiah there, then on the 12th at the Saint-Roch Church (tickets from 25 to 30 euros).

Saint-Roch, an 18th century church boasting a museum-worthy art collection, 10 minutes from the Louvre, has an early (but no less excellent) Cavaillé-Coll, from 1842. On Mondays from 12:30 to 1:15 p.m. there are “Musical Monday” concerts when you can hear the organ; you can also hear it at some masses.

A Cavaillé-Coll organ and the Notre-Dame choirs are not the only markers of a great Paris church music experience. On the Left Bank’s Boulevard St.-Germain is St.-Germain-des-Prés Church. This church with delicious acoustics is the oldest in Paris, founded by King Childebert I in 543, restored many times and now completing a major multiyear renovation.

After decades of water damage and grime, the decorative Italianate wall paintings and murals of Hippolyte Flandrin have emerged in brilliant color; as have marble columns, delicate vaulting, mosaic floors and a gilded copper-clad roof that reflects the sunlight.

On Christmas Eve at 10 p.m. a musical prelude to the 10:30 p.m. mass is scheduled. On the 25th and 26th of December, the planned masses are at 11 a.m. and 7 p.m., during which traditional music will be sung with the Christmas liturgy. There is also a Christmas concert scheduled on the 25th at 3:30 p.m. (no reservation necessary and free, though a donation is encouraged).

Some churches with high tourist appeal offer concerts of uneven excellence. Ste.-Chapelle, just steps away from Notre Dame on the Ile de la Cité, advertises concerts with a recognizable repertoire (Vivaldi’s Four Seasons is a favorite). The performances are considered good enough — for tourists. The cost is not insignificant: about $70. Pay $10 more for a coupe of champagne.

From Dec. 19 to 30th (except Christmas Day) Christmas concerts are planned at Ste.-Chapelle; also, two New Year’s concerts, on the 31st and January 2nd. (Some dates have already sold out.)

Ste. Chapelle has not been used as a church since the French Revolution, but like Notre-Dame, is one of the world’s most glorious examples of Gothic architecture, and it still resembles the grand place of worship it once was.

Light pours in from Ste. Chapelle’s stained-glass windows covering more than 6,000 square feet, most of them dating from the 13th century. A phone app allows visitors to zoom into every stained-glass panel for one of the most uplifting experiences of discovery in all of Paris: Biblical stories — including Genesis, Exodus, Ezekiel’s visions, Judith’s beheading of Holofernes — told in glass.

Ste. Chapelle also has a 19th-century lead-covered wooden spire, a third of the size but not unlike the one on the roof of Notre-Dame that collapsed in the fire. The Ste. Chapelle version was created in 1853 by Adolphe Victor Geoffroy-Dechaume, an architect colleague of Eugène Emmanuel Viollet-le-Duc, who erected the Notre-Dame spire. If you stand at just the right spot at the far end of the courtyard outside Ste. Chapelle, you can get a perfect view, as well as a reminder of what was lost not far away.

The spirit of Notre-Dame touches unexpected places. Many biblical texts describe heaven as a place of music, and for English-speakers in Paris, an earthly version can be found at the American Cathedral across the street from the Crazy Horse nightclub in central Paris. An Episcopal Church built in 1886 and designed by the English architect George Edmund Street, it has an English-language liturgy, as well as a Cavaillé-Coll organ, of which it is very proud. The Cathedral has launched a fund-raising campaign to restore the instrument.

The cathedral livestreams its services, a practice it began during the pandemic lockdowns. Professional singers donate their time and join in with the choir. Its “jewel in the crown,” according to Zachary Ullery, its musical director, is a 45-minute, mediative “Evensong” service on select Sundays at 6 p.m. There is also a free concert every Sunday afternoon at 3 p.m.

For Christmas this year, a jazz Vespers is planned on Dec. 11th at 8 p.m., as well as “Christmas Lessons and Carols” on the 18th and 19th. On Christmas Eve, the 10 p.m. service is expected to feature carols for all to sing.

“If you want to hear a really great organ, come to the American cathedral,” said Mr. Ullery. “Come if you want to hear Requiems and English Renaissance motets. It’s hard to find a sound like this anywhere else in Paris.”

Charlotte Force contributed research.

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By Indana