When the group of singers warmed up on stage, they rolled their shoulders back and forth, stretched their arms, and shook off the day’s stress. They took deep breaths, filling their lungs and straightening their backs. But it wasn’t a quiet exhale that filled the Old Whaling Church in Edgartown. It was a cascade of notes falling over each other in harmony, going from high to low.

Aaaaaaaaahhhhhh.

Barbara Lopes and daughter Robyn Lopes-Beaulieu in the soprano section. — Ivy Ashe

For the next two hours, the harmonies continued, as the 115-member Island Community Chorus practiced for its annual holiday concert, which takes place this Saturday and Sunday. Rehearsals for the program began this fall.

“You only have so many weeks to prepare, and so every week is precious,” said chorus director Peter Boak. Meeting the deadlines is his biggest challenge, he said.

And the choir is up to that challenge.

“It’s conducted in a very professional manner,” said soprano Barbara Lopes before rehearsal. “We’re treated as though we’re professional singers — in a very gentle way. [Peter] coaxes us into doing some amazing things with some difficult music.”

This year’s program features more light fare than previous concerts — a bouncy arrangement of Jingle Bells highlighted by soprano Molly Conole’s solo, for example — but still spotlights the technical abilities of the choir.

Peter Boak will once again direct the chorus. — Ivy Ashe

“The Gift of the Angels is a very challenging piece,” Mrs. Lopes said. “It’s very beautiful. Lovely melodies, lovely harmony.”

Mr. Boak dug into the chorus’ archives to create the eight-song lineup. “It’s a pretty extensive library,” he said.

The Island Community Chorus got its start in the mid 1990s. Before its inception, singers came together to sing in Abendmusik or the Martha’s Vineyard Chorus. Barbara Lopes and her husband Carl met while singing with the Martha’s Vineyard Chorus, and had their first date the night of a Christmas performance some 30 years ago. Mrs. Lopes’ parents were also choir veterans.

“I was in [the chorus] years ago, and then, you know, family happens, life

happens,” Mrs. Lopes said. “I’m so glad to be back.”

And family is back, too. Her sister Carolee Stewart sings with the group, as do her children Robyn Lopes-Beaulieu and Dorian Lopes.

“It’s a really friendly group of people. Everyone’s very welcoming,” said Ms. Lopes-Beaulieu. A Minnesinger in high school, she said she was enjoying the Jingle Bells arrangement in particular. She performed the same arrangement with the Minnesingers as a first soprano.

Across the aisle from the Lopes family, in the alto section, sisters Seniel Hannagan and Leandra Seward flipped through their music sheets. Ms. Hannagan started singing last year, when brother Jesse Seward joined. All three of the siblings were Minnesingers.

Seniel Hannagan and sister Leandra Seward sing alto. — Ivy Ashe

“I just missed singing,” Ms. Hannagan said. “I missed singing with a choir, and I missed following a director.”

“Peter Boak was my music director at the Tisbury School,” Ms. Seward added.

“I think people get intimidated because they think they have to try out, but you don’t have to try out,” Ms. Hannagan said.

You do have to be prepared to put the time in on each piece, though. Mr. Boak “pushes us constantly to get us to the next step, so we’re not complacent,”

Mrs. Lopes said. “It keeps us on our toes.”

During rehearsal, Mr. Boak and the chorus continued to fine-tune each piece in anticipation of the weekend. “I don’t think you can be too loud right there,” Mr. Boak said during a section of The Holly and the Ivy. Occasionally he walked to the back of the church to see how the songs sounded from different locations.

“A lot of you are still a little serious,” he commented. “This is not . . .” he paused for effect, “Handel.”

The Island Community Chorus performs its holiday concert on Saturday, Dec. 6, at 7:30 p.m., and Sunday, Dec. 7, at 3 p.m. Both shows at the Old Whaling Church in Edgartown.