On the school’s Alumni Sunday Nov. 9, members of the Archdiocesan Choir School community unveiled a 40-pound, 29-inch by 28-inch stained glass window of the school’s coat of arms, first sketched by the late Pilot illustrator Gerry Rooney.

The window was mounted Nov. 11 along the walkway that connects Harvard Square’s St. Paul Church and the building that houses the choir school, the parish center and the Newman Center serving Catholic students at Harvard University, said Andrea J. Roy, whose son Gabriel C. Liguori graduated in June 2008 and now attends Boston College High School.

The walkway overlooks the church’s brick courtyard and is the path that the students, all boys in grades five through eight, take at 7:50 a.m. on their way to sing at Mass, Roy said. They sing every school day except for Thursday, when they have gym.

Theodore Marier founded the school in 1963 to revive the singing of Gregorian chant. Marier led the school until 1974, when he was succeeded by John Dunn, who was one of the original faculty members and who retired with the class of 2008. The current headmaster is Jennifer Lester, who is also the founder of the Seraphim Singers.

Roy said that as her son’s graduation approached she was looking for an appropriate gesture and came upon the idea of enlivening the school’s crest, which had always been shown in black and white or maroon, the school’s color. The window was the gift of the students and parents of the class of 2008.

With the help of the new pastor, Father Robert J. Congdon, she researched the school’s crest in the parish and school archives and contacted The Pilot to determine if Rooney, a long time St. Paul’s parishioner, had ever made a more detailed drawing or had ever used color.

Finding nothing beyond what she had and Rooney’s own brief description of his design, she announced the project during the graduation events for her son’s class.

One of the challenges of making the stain glass was finding the proper artist, she said. “There are many stained glass companies, but few work in liturgical art, even fewer were of the quality that I was looking for.”

Eventually, Roy said she selected Philadelphia-based artist Joseph Beyer, who was excited about the product and able to produce a piece that would complement the Munich School-style stained glass program of the church.

One tribute to the church’s stained glass is the square crosses in the corners of the window, which were not in the Rooney design, she said. In St. Paul’s transom windows depicting the doctors of the Church, there are small Maltese Crosses.

Roy used small symmetrical crosses, in the style of the Jerusalem Cross, that recall the wooden crosses the boys receive with their white surplice on the third Sunday of their first year, Investiture Sunday. To receive the cross, the students pass the school’s requirements to be a full-fledged member of the choir, she said.

Other elements of the design were decisions Roy said she made based on her own studies of European heraldry. The green field refers to the choir’s signature song “Gaelic Blessing,” which was adapted from St. Patrick’s Breastplate by John Rutter.

“The blue bands behind the shield were a thematic adaptation of the field color of the coat of arms of Dom Prosper Gueranger, the 19th century monk who founded Solesmes Abbey in France and revived the liturgical use of Gregorian chant,” she said. It was the music of this abbey that inspired Marier to his life’s work.

“The window was created to memorialize Marier and the other dedicated instructors who have gone to their rest, honor the service of John Dunn and to celebrate 45 years of the Choir School,” she said.