On Saturday, their public debut at Evensong will end centuries of all-male tradition.
Canterbury is not the first British cathedral to set up a girls' choir, but as the mother church of the 80 million-strong Anglican Communion—one struggling to define the role of women in its ranks—its move has special resonance.
That is not lost on the 16 girls, aged between 12 and 16, who have been chosen to make this bit of history.
"That's an amazing thought in the back of your mind—no girl has sung in this cathedral over an amazingly long period of time," said 12-year-old choir member Abby Cox. "I've always liked singing, but I think this is the major event that has happened in my life and I'm so excited to be part of it."
The choristers attend several local schools and were chosen at auditions in November. Unlike members of the Canterbury boys' choir, who live at the cathedral and rehearse every day, the girls come together just once a week.
Despite their limited rehearsal time, choir director David Newsholme said the girls are focused and enthusiastic about the psalms, anthems and responses they have to learn.
"We've had to learn it quite quickly, but it's just so fun to be in here you don't really think about that," said Cox. "You are making music with girls that are as passionate as you are."
Girls' choirs are not a complete novelty in the Church of England—Salisbury Cathedral established one in the 1990s and several other cathedrals have followed. Female voices have occasionally been heard in Canterbury Cathedral as part of visiting choirs.
But they still attract notice in an institution that values its traditions and changes slowly. Anglicans are still seeking an elusive consensus on the divisive issues of female bishops and gay clergy.
Singing girls have their opponents, too, including one group called the Campaign for the Traditional Cathedral Choir, set up to "champion the ancient tradition of the all-male choir."
Tradition is especially important at Canterbury, about 60 miles (100 kilometers) southeast of London, whose archbishop heads the Anglican church. Founded in the 6th century—although most of the spiky Gothic building dates from later in the Middle Ages—it has been an important place of Christian pilgrimage since Archbishop of Canterbury Thomas Becket was murdered here in 1170 by knights loyal to King Henry II.
Dean of Canterbury Robert Willis said music has been sung in the cathedral since it was founded—first by monks, then by a choir of men and boys set up more than 1,000 years ago. He stressed that a female choir was "a natural development" that adds "diversity and richness" to the cathedral's traditions.
"Nothing of the old tradition is damaged," he said. "It's being enriched, enlivened and developed."
The girls' choir will perform initially when the boys take a break each term, but Willis said the girls will eventually play a bigger role.
"And occasionally I'm sure in the future, both of the choirs will sing together on festival occasions," he said.
That is music to the ears of 16-year-old chorister Poppy Braddy.
"I think this is just the beginning of something new," she said. "I think it will encourage the church forward. I don't think there is anywhere that women should be limited."
At a rehearsal Wednesday night, the choristers arrived in jeans or school uniforms, chatting and laughing as they changed into long purple cassocks. During services, they will wear white surplices over the robes.
They rehearsed in a small, stuffy music room at the top of a narrow staircase in one corner of the cathedral. Its walls are several feet thick, lined with shelves full of sheet music by Mozart, Bach, Benjamin Britten and others.
Their high voices mingled as Newsholme coaxed the girls through an anthem by 19th-century composer Samuel Sebastian Wesley: "Who can express the noble acts of the Lord?"
"Even more eye contact," he encouraged the singers. "Even more clarity."
They seemed all ready to go for their historic debut—except for the rubber toes of Converse sneakers peeking out from under their robes.
"I'll have a word with them about that," Newsholme said.
Jill Lawless can be reached at http://Twitter.com/JillLawless