In the world of choral music, an accompanist must never stand out.

“I consider myself one of the group. A good accompanist is inconspicuous,” said pianist and organist Garrett Brown of Oak Bluffs, who marks his 20th year of rehearsals and performances with the Island Community Chorus at this weekend’s holiday concerts in Edgartown.

It’s the same thing on Sunday mornings, when he plays organ and directs the choir at Trinity Worship Center in the Methodist campground.

“You’re part of the whole experience,” Mr. Brown said.

Mr. Brown has been an essential part of the Island Community Chorus for so long that chorus director Peter Boak now considers him a “co-director.”

Peter Boak directs the chorus and calls Mr. Brown his equal partner. — Mark Alan Lovewell

“He’s like an equal partner, that’s what I would say,” added Mr. Boak, who roomed with Mr. Brown’s older brother Wesley at Westminster Choir College in Princeton, N.J.

“Whenever my brother came home, Peter was with him,” Garrett Brown recalled. Later, the youngster would attend Westminster himself.

Mr. Boak introduced the Brown brothers to Martha’s Vineyard, where Wesley settled first with his wife and Garrett followed in the late 1990s. Mr. Boak, who had revived an earlier all-Island chorus and established it as a nonprofit in 1998, was in need of an accompanist and the younger Mr. Brown—who was 10 when they’d first met—fit the bill.

“He’s just a consummate musician,” Mr. Boak said. “His musicianship is flawless.”

In his early years with the chorus, Garrett Brown took the duty of transparency so seriously that “he hardly ever talked,” Mr. Boak said. “He came in, did his accompanying and went home. Then, as the years progressed, he started helping us find repertoire. He started speaking up at rehearsals when he heard something I missed or the chorus missed.”

It was Mr. Brown’s idea for the chorus to sing the Hawaiian Christmas song Mele Kelikimaka this weekend at the

Old Whaling Church, complete with ukuleles, Mr. Boak said.

Another holiday tune Mr. Brown suggested with the chorus playing kazoos didn’t fit into the program for this year, might turn up in the holiday 2020 show.

Raised in the Methodist church with a minister father, Mr. Brown is steeped in hymnody but enjoys many other kinds of music as well. “The one thing I don’t listen to is modern jazz. I can’t stand it,” he said. “Otherwise I listen to everything. When I do a playlist, it’s stuff from every genre.”

Soprano Pam Butterick, the chorus’s board president this year, has been singing with Mr. Brown for most of his two decades with the group.

“He’s fabulous,” she said. “He’s steadfast and he practically has to play an orchestral reduction, including all the parts. He reads Peter’s mind.”

“He’s Peter’s right and left arm, which leaves Peter’s arms free to direct,” Ms. Butterick continued.

Over his two decades with the chorus, which also performs annually in April at the Old Whaling Church and on July 4 at the Tabernacle in Oak Bluffs, Mr. Brown said he’s seen a major improvement in the singers’ musical skills.

“When I first started, they weren’t good sight readers, so there was a lot of note-banging,” he said. “They have become incredible sight readers. They could almost sight read anything.”

And they have helped him grow musically as well, Mr. Brown said.

“My experience with the community chorus has made me a better musician because of the incredible variety of things that we do and perform. It has just made me a better musician.”

Apart from the occasional organ recital years ago, Mr. Brown said he has never had a desire to step into the spotlight on his own, choosing instead to support the singers.

“That is my passion, more than anything else,” he said. “Absolutely.”

The Island Community Chorus performs its holiday concerts at the Old Whaling Church in Edgartown Dec. 7 at 7:30 p.m. and Dec. 8 at 3 p.m. For more information, visit