(The Christian Science Monitor) On a recent Monday evening, tourists and locals dining at restaurants next to Leipzig’s St. Nicholas Church heard a faint brass band sound accompanying their conversations.

The foreign tourists among the diners had no idea what the brass music was about, but the local diners were accustomed to it. Monday night is rehearsal night for the St. Nicholas Church’s trombone choir, one of about 30 such ensembles in Leipzig alone.

“I’ve played in brass bands in the past, but trombone choirs are great because you play with people of all ages, and you play all kinds of music,” said Silke Lan­tau, a young member of the St. Nicholas trombone choir, after the rehearsal.

Lantau, an 11-year veteran of her instrument, plays the trumpet. Although the name suggests that trombone choirs only feature one instrument, they are in fact church brass bands set up the same way as church choirs, with sopranos, altos, tenors, and basses.

While membership in Germany’s Protestant (Lutheran) church is rapidly declining—last year a record 200,000 members left the church—its trombone choirs are thriving. Today, Germany has 110,000 amateur brass players belonging to 6,000 trombone choirs.

In early June, thousands of trombone choir members from all over the country gathered in the eastern German city of Dresden. Registration was up from the last such festival eight years ago.

Nobody is quite sure why the bands are called trombone choirs rather than, say, trumpet choirs or brass choirs. According to one theory, the name is connected to Martin Luther’s translation of a biblical instrument, unknown in 16th-century Germany, as a trombone, which was an instrument familiar to Ger­mans. Another theory holds that the first trombone choirs used the name as a way of distinguishing themselves from secular brass bands.

“Trombone choirs became popular about 100 years ago, during the Protes­tant revival movement in Germany, when lots of churches moved their ser­vices outdoors and needed accompaniment,” said Reinhard Gramm, a board member of Germany’s association of trombone choirs. “But today churches have both organs and trombone choirs in their services.”

Christoph Käßler, a hobby trombonist who has led the St. Nicholas trombone choir for the past 13 years, has seen membership grow even as service attendance has plummeted from 1989, when St. Nicholas peace prayers spawned the demonstrations that led to the fall of the Berlin Wall. When Käßler arrived, the trombone choir had 13 members; today it has 30, including young teen­agers, college students, young professionals, and retirees.

“Making music together gives people a sense of community,” he said. “You arrive not knowing anybody and make new friends.”

Indeed, according to a recently published study by Julia Koll, a theologian at the University of Göttingen, trombone choirs are also unique among German hobby associations in bringing people of all ages together. When Koll’s first results—a survey of trombone choirs in the Hannover Diocese—were released three years ago, the diocese’s leading official explained that the brass ensembles are an area where the church has no recruitment and retention problems.

“People don’t just join trombone choirs because of their Christian faith,” Gramm said. “They join as much because of the music. We try to perform all kinds of music.”

Christian Hälfer, a young trombone player at St. Nicholas, has only played the trombone for a couple of years and has already played in a brass band. But, he explains, the trombone choir gives him the opportunity to combine his faith with music.

At their rehearsal the St. Nicholas trombone choir—featuring mighty trombone and trumpet sections, along with one horn and two tubas—practiced hymns, brass band pieces, and popular music with syncopation that tripped some players up.

Trombone choirs don’t always make an impeccable sound. Like most church choirs, there are no auditions, and even players new to their instruments are encouraged to join, with beginners offered coaching on their instruments.

But with at least a couple of experienced players in every section, trombone choirs manage to perform pieces ranging from chorales to gospel and brass band classics at church services and community concerts. The St. Nicholas trombone choir, for example, performs 35 times per year, including monthly church services as well as performances at retirement homes and the city’s Christmas market.

Lantau, one of St. Nicholas’s best trumpeters, patiently repeated sections with less experienced players. Although she played in a brass band for several years, she says she prefers the trombone choir because of its variety of ages. At the rehearsal she shared a stand with a retired man.

This article was edited on June 20, 2016.