Roy Ramthun, center back, was one of the 90 people chosen to be a part of the Archdiocesan Papal Mass Choir who rehearses for the first time together at St. Mark the Evangelist Catholic Church in Hyattsville, Md. (Katherine Frey/The Washington Post)

Tears welled in Roy Ramthun’s eyes when he thought about the honor he had received.

“It’s a little emotional,” he said as he stood holding a hymnbook outside a suburban Maryland church last week .

Ramthun, 53, of Silver Spring, was one of 90 singers chosen for an elite choir assembled from across the region to sing at Pope Francis’s Mass this month in Washington.

The choir is the biggest of the five singing at the huge outdoor service.

This was the first rehearsal.

See details on each of the events in the Pope’s visit

The members gathered at St. Mark the Evangelist Catholic Church in Hyattsvillewith their pencils, water bottles and white loose-leaf binders filled with music.

They were elementary school music teachers, local choir directors, members of the clergy, singers in parish choirs. Most had never sung together, and many more had never met.

They had been chosen at 15 special auditions last spring from a group of 330 applicants.

They picked up name tags beside a life-size cutout of the pope, at a table bearing signs that said “soprano,” “alto,” “tenor,” “bass,” and filed into the church’s front pews beneath a huge crucifix suspended from the ceiling.

And as choir director Tom Stehle led a rigorous 2½-hour rehearsal, the choristers’ voices filled the church with Gregorian chants, old-fashioned hymns and songs from the pope’s native Argentina.

The pope is scheduled to celebrate Mass, largely in Spanish, Sept. 23 on the lawn of Catholic University facing the east portico of the Basilica of the National Shrine of the Immaculate Conception.

The 90 hand-picked members of the Archdiocesan Papal Mass Choir rehearse for their upcoming performance at the Mass to be celebrated by Pope Francis at the Basilica of the National Shrine of the Immaculate Conception. (Katherine Frey/The Washington Post)

“This is the opportunity of a lifetime,” Ramthun, a tenor who sings in the choir of St. John the Baptist Church in Silver Spring, said before the rehearsal last Monday night. “I’m just overjoyed.”

Kristin Brown, 26, of Kensington, is a music teacher, member of the choir at Holy Redeemer parish and a soprano.

“I was on the waiting list,” she said. “So I didn’t get on [the choir] until they [said]: ‘Hey, someone got out. So how about you come on and sing for us?’ ” she said. “I found out about a month-and-a-half ago.

“I’m so excited,” she said. “Just to be in the presence of Pope Francis is one of the most exciting things. I love his values. I love everything he’s about. I think he’s a great pope.”

Karen Rappaport, 33, of Washington, is a music teacher at Beauvoir, the National Cathedral Elementary School, and an alto.

She said she was in the choir when Pope Benedict XVI said Mass in 2008 before 40,000 people in Nationals Park.

“It was just an amazing experience,” she said. “What I teach my kids is it’s really important to be a part of something that’s bigger than yourselves, bigger than your community.”

Asked her reaction to being picked this time, she said, “I posted it on Facebook.

“I’m excited to be a part of something so big,” she said. “It’s such a blessing to be able to do what I love and do it in such a grand scheme and reaching out to so many people.”

The Archdiocesan Papal Mass Choir is directed by Stehle, the main music director for the Mass and the music director at Washington’s Cathedral of St. Matthew the Apostle.

Preparations have been intense, Stehle said. No rehearsal absences are permitted. Anyone who misses is replaced.

As he directed the practice, aides walked around the choir — one in the front, one in the back — listening for flaws. An assistant held up colored cards to tell Stehle time was expiring for practice on a segment.

After the rehearsal was over, Stehle and his assistants huddled at a Hard Times Cafe and compiled detailed notes. “It’s measure by measure an analysis about what happened, what needed to improve,” he said later.

“We closed the place,” he said. “We were the last people there.”

The notes were e-mailed to the singers last Saturday.

The choir rehearsed again Monday and was greatly improved, Stehle said in an e-mail. “It was like a different choir,” he said. There are four more rehearsals before the Mass.

Speaking before the practice last week, Stehle said the choristers have been practicing at home or in small groups, but “we’re really on a journey now that’s going to take us to that day.”

He said the goal is “a profound prayer, not just a spectacle, not just a musical moment. . . . [but] something that will profoundly affect all those who are there worshiping together.

“Our purpose is to engage the assembly,” he said, “to unleash the song of the heart of the people.”

The choir’s music list includes arrangements of “Simple Gifts” and “Zion’s Walls” by American composer Aaron Copland, songs by Argentine composer Pablo Sosa, as well as Latin acclamations and hymns.

“We’re trying . . . to catch the spirit of our new pope and his roots in Latin America and his roots of being in the Western Hemisphere,” Stehle said.

As the choir assembled in the church, Stehle stood on the steps of the altar. He was firm as he put the choristers through their paces.

He rapped the lectern with his baton for attention.

“Eyes,” he said at another point. “That way I know you’re listening. Can I have your eyes, please?”

During one piece, he admonished the basses: “If you can’t hit that top note, don’t sing it.” And to the sopranos and altos: “Don’t oversing. Don’t push it.”

He was also complimentary: “Sounds beautiful. No one would ever believe you’ve never sung together. Just beautiful.”

Choir members were intent, scribbling notes on their music. During intervals, Diana Sáez, founder and artistic director of the Washington Latino chorus Cantigas, drilled them on Spanish pronunciation.

“Jesus” is pronounced “HEY-soos,” she pointed out. “Cabeza” — head — should be said “ca-BAY-sah.” And “Dios” — God — should be pronounced with a soft D.

As the choir members worked, darkness fell, and cars whizzed by outside on Adelphi Road.

Stehle had them go over Pablo Sosa’s “Este Momento en Punto” — “This Is the Moment” — with its refrain, “La rai, la la rai, la ra.”

Earlier, the choir had rehearsed Sosa’s “El Cielo Canta Alegria” — “Heaven Is Singing for Joy.”

As they did, it began to pour rain, and lightning flickered through the church windows.

“Ah . . . the heavens are singing,” Stehle said. “Perfect timing.”

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