"One reason the hymns of yesteryear are not appreciated is because they're not sung well," Conway said. "There is nothing worse than an anthem sung poorly. But Marco's group sings powerfully and well. He has attracted an outpouring of musicianship from all over the city."

The Community Concert Choir is a mature ensemble — "mostly 45 and older," Merrick said — with several retirees in the mix, among them Dr. Nina Rawlings, mother of Baltimore Mayor Stephanie Rawlings-Blake. But the energy level can sound decidedly youthful, especially when the tempo quickens.

"You become one with the music, the way Marco leads us," said Marian W. Gayle, a soprano in her 70s who is president of the choir. "His command of the whole group is terrific. We are so thrilled and blessed that we have this. We went from 75 members at our first concert to almost 150 now."

One of the newer members is Gayle's daughter, Heather E. Gayle, a financial adviser with a New York Life Insurance Company office in Columbia. She started as a choir booster, lending a hand with the large auxiliary group that helps raise money for the organization.

"This year I started singing with the choir," the younger Gayle said. "A lot of the older music was a learning curve for me, but it doesn't feel like work. And I love how Marco gives you context."

As when Merrick tells the choristers the meaning of an inspirational song from 1868 that will be on Sunday's program, "The Long Day Closes," a tender piece in four-part harmony by Arthur Sullivan (best known for his collaborations on operettas with W.S. Gilbert).

The lyrics, by Henry Fothergill Chorley, contain images of a "half awake" moon, "gray mist creeping," and a clock that has "ceased to sound."

"I used to think it was just a beautiful poem about a day," Merrick said, "but I realized it is about life, which is a long day. We come here, live a day, and transition off at sunset. I like telling the stories behind the pieces. It helps the choir to embrace the music in a real way."

And if his singers don't embrace the music as wholeheartedly as he does, he lets them know it. At one point, when he didn't sense enough expressive nuance from them in "The Long Day Closes" at the line, "Go to the dreamless bed where grief reposes," the director didn't let it pass: "What bed are you all in?"

He wasn't too pleased, either, when voices entered haphazardly singing about the ceasing clock.

"Everyone has a different clock. I can tell that by how late you come to choir practice," Merrick said to a smattering of laughs.

He got more laughs when, working on "Ride the Chariot," he asked for a dynamic delivery of the words "My Lord." The reverential approach by the singers just would not fly.

Merrick finally gave them an example of what he meant (it was the weekend of the gigantic Powerball jackpot): "I just won $600 million — my Lord!" That did the trick. On the next try, the chorus punched out those words with infectious spirit.

The fast-talking, fast-moving director maintains a mix of informality and seriousness at rehearsals, but the balance is clearly on the serious — and the sincere.

Merrick has been on his give-me-that-old-time-religious-music mission for a long while. His first big outlet was a choir he formed at Douglas Memorial Church; the group performed traditional repertoire at annual concerts for 12 years but ceased in 2010.

"I would run into people for months who would tell me, 'You need to do this somewhere else; you need to start something in the community,'" Merrick said. "I kept saying no, but you can see the result of my saying no."

The youngest of seven children, Merrick got early exposure to this music sitting in the balcony for services in a Southwest Baltimore church.

"My mother remembers that hearing the organ would always get my attention," he said. "I wouldn't be distracted. Then I started paying attention to the singing. That's how it all started."

Merrick went on to study piano at Peabody Preparatory when he was about 8 (he teaches piano now at the Nathan Carter School of Music at New Shiloh Baptist Church).

He eventually focused on communications, earning degrees in that field from Towson University and the University of Baltimore, and worked locally with WJZ-TV and a Boston station over the years. He also taught communications at Morgan State. His current day job is with Baltimore City's Register of Wills.