BOSTON -- On Oct. 9, Xavier Trevor wound his way up a dizzying spiral staircase inside the Cathedral of the Holy Cross until he reached the choir loft.

The massive stained-glass windows were practically on fire from the late afternoon sun. Above Xavier loomed the Gothic façade of the cathedral's 5,292-pipe Hook and Hastings organ, which he was to play for the very first time. The 13-year-old removed his sneakers and put on a squeaky pair of immaculately shined black dress shoes. They're his "organ shoes," narrow enough so he doesn't hit more than one pedal while playing.

The organ's bench was too high for Xavier, so his tutor, cathedral Music Director Richard Clark, lowered it to suit his height. Xavier sat, and his hands began to gently glide along the keys. The low rumble of Louis Vierne's Preambule rippled through the gaping sanctuary, followed by the heavenly clarity of higher notes.

As Xavier played, he gazed at the cathedral's intricate vaulted ceiling and thought of the many times he had practiced and played the Preambule, one of his favorite pieces. He had to free his mind to contemplate the multitude of sounds that the organ could produce, depending on which of its over 70 stops he decided to pull.

"Whenever I hear an organ from downstairs or on the ground, not in the loft, I always like to look up at the organ," Xavier said. "I don't know. I get lost in thought when I look at organ pipes and facades of the organ."

The final note, a low C, bellowed out of a 32-foot pipe, the organ's longest.

"It's like hugging a tree," Clark said. "It's the size of a tree to produce that low C. You feel it more than you hear it."

Xavier had never played in such a large space before. The eighth grader at St. Paul's Choir School in Cambridge said that the cathedral's 150-year-old organ is already one of his favorites.

"It's a different experience every time I play a different organ, and it's definitely one that I'll remember," he said.

Xavier is one of three young organ scholars who will perform at the cathedral's 36th Annual Organ Benefit Concert on Oct. 19 at 3 p.m. Xavier will perform the Preambule, the epitome of the French style that he enjoys in organ music.

"It's under my fingers," he said of the piece.

"Wonderful expression," Clark said of Xavier's playing. "And he really is singing, so to speak. The music is singing forth from his fingers."

Xavier began playing the organ in 2023. The organ isn't exactly a household instrument, so he plays in an "organ practice room" two or three hours per week.

"As a chorister, I was always looking at the organist Burtner, who, like Xavier, is a student of the American Guild of Organists' Young Organist Initiative, and Clark's own son, Anthony.

Clark knows the challenges of being a professional musician firsthand and expects that his son will have to endure the same. Still, he is proud of Anthony.

"It's great," Clark said. "It's what God calls you to do."

Anthony, a 16-year-old sophomore at Xaverian Brothers High School in Westwood, joked that he has "a good head start" on his father, who didn't begin playing the organ until much later in life. Anthony grew up watching his father play, and during his years as a student at St. Paul's, listened to the organ daily.

"It's really hard not to be interested in it because it's such a cool instrument," he said.

He plays in the cathedral about once a week, and played during Mass each week over the summer. He performs daily on a "practice organ" in his home.

"The sounds are really cool, especially being in the right building," he said. "The cathedral is a lot of fun because it has a lot of reverberation, so if you play really loud, it sounds really cool and makes you feel really good about yourself."

As a Catholic, he considers it his duty to perform. He feels that he is not playing for himself but for God.

"It has this heavenly sound that really makes you feel like Jesus is present, and also because it's incredibly versatile," he said.

When he grows up, he wants to be a professional organist -- to start. Someday, he'd like to be a conductor or music director, especially at St. Paul's.

Burtner, an 18-year-old senior at The Victor School in Acton, has been playing since 2023. His mother showed videos of him playing piano to her friends, one of whom was an organist who is now Burtner's teacher. She recommended that he apply for the Young Organist Initiative.

"I love the quality of the sounds," he said of the cathedral's organ, which he has played twice.

He's nervous for his recital and plans to practice as much as he can beforehand.

"I feel like there's a spiritual component to playing the organ," he said. "I feel like you can convey so much with the instrument. I think it has the power to reach people."