SOUTH END -- Hundreds of worshipers joined Cardinal Seán P. O’Malley to celebrate the Nativity of Our Lord at midnight Mass in Boston’s Cathedral of the Holy Cross Dec. 25.

Before the liturgy began, the cathedral’s parish choir, conducted by Leo Abbott and featuring soprano Diana Doyle as leader and psalmist, performed traditional Christmas carols to the darkened cathedral.

Save for the 10-foot candles of the Advent wreath, the choir, draped in white vestments and soft shallow lamps, were the only element visible to the people filling the pews.

Shortly before the clock reached midnight and the start of Christmas, the cathedral’s rector, Father John Connolly, rose from the pews, stood beside the wreath, bowed to the altar and briefly retired to the sacristy.

Suddenly, the entire cathedral was bathed in light. The magnificent white altar, bedecked with evergreen boughs, poinsettias and red and white floral arrangements, burst from the shadows.

Ushering congregants emerging from the narthex to the nave, was a member of the Knights of Malta, John J. Hurley, dressed in his cape and medals, handing out worship guides.

Hurley said he is a 25-year member of the cathedral parish community and every year he has volunteered his services for the Christmas midnight Mass. “That is what it is all about, isn’t it?” he said.

His thoughts were affirmed in the cardinal’s homily. “Midnight Mass is a call to stark realism,” said Cardinal O’Malley. “It is so powerful, so beautiful. It far surpasses our tinsel-laden reality.”

“The real joy of Christmas is that there is a real reason to celebrate,” the cardinal said. “Avoid spiritual Alzheimer’s,” the cardinal exhorted. Instead, he said, remember that the message of the first Christmas carol, sung by the angels: “Glory to God in the highest,” is a call to worship.

“Celebrate Christmas as they did with praise and worship. Then, it will not fade on Dec. 26. It will only grow stronger.”

Despite the hour, the liturgy was punctuated by the sounds of children. Some laughing. Some crying.

It was the first Christmas for five-month-old James Clifford, said his mother, Christina M. Clifford of St. Patrick Parish in Groveland.

Although the two finished the service by the entrance doors, Clifford said she was happy her son made it through the readings before it was time for him to take his leave.

As James struggled in her arms, his mother said she and her husband, J. Brandon, created a special family time attending the Mass together, as well as, getting the chance to hear the cardinal preach.

Another set of parents sat in the front pews facing the choir, Leo and Carol Doyle. The Doyles, from St. Patrick’s Church in Stoneham, came to hear their grown daughter, Diana, sing at her 10th midnight Mass of the Nativity, her mother said.

From the pulpit, Diana sang both the opening proclamation of the “Roman Martyrology” and the general intercessions.

The martyrology, a chanted litany of important events in history before the birth of Jesus and their years before His coming, is the more difficult for her because of her fear of getting the number of years wrong, said Diana.

Performing at this Mass is her personal tradition, she said. “I want to spend the holiday with my musical family.”

Her proud parents, gathering their coats, said they never miss it.