It’s a haunting sound when a group of boys’ voices in the treble range convene.

I’m not talking about performances by boychoirs, which feature the unchanged voices of prepubescent boys, who together make a sound so lovely and pure that the effect is haunting.

I’m talking about the start of boychoir practices and the scary sound created when a gaggle of rambunctious dudes with short attention spans and constant jokes get together to learn the craft of choir singing.

But for 30 years, the ever-patient Dr. Thomas Strode has led the Boychoir of Ann Arbor through innumerable practices, and his ability to keep cool and impart high-quality musical education to a rather wiggly and easily distracted audience is remarkable.

In the common area of Ann Arbor’s St. Paul Lutheran Church, where Strode is the director of music, he teaches boys musical theory and gives singing lessons using a quiet, measured tone of voice. Under Strode's gentle guidance, the boys' constant hum of silliness at the start of practice soon becomes a gloriously soothing sound when they begin to sing.

Strode instructs a prep choir, for newer singers, as well as the performing choir, which features more experienced vocalists and expands the treble boychoir model to also include an SATB (soprano, alto, tenor, bass) choir, with the older boys and their changing voices providing the lower notes.

Dr. Strode really understands how to teach children, which is why Boychoir of Ann Arbor has thrived for three decades. And the kids really do learn to sing beautifully, as listeners will be able to hear at the “A Boychoir Christmas” concerts on December 9 and 10.

These annual shows are highlights for many holiday concertgoers -- but they will also be Strode’s final ones as the choir’s director. He’s retiring at the end of the boychoir’s season, which wraps on June 4 with the “Spring Finale” concert.

With this being Strode’s final Christmas concert, we asked the good doctor to give us a preview of what we will hear and why.

Q: The choir prepared 16 songs for the concert. Which one was the hardest for the kids to master and why?
A: There are two works that I would consider more difficult in this concert, for different reasons:

“Stille Nacht” as arranged by Philip Lawson for the King’s Singers. It is in six voice parts, a cappella, with key changes, and in German. Balance, blend, and dynamic contrast are some of the issues we’ve been working on in this piece.

“The Shepherds Sing” by Bob Chilcott. Shaping of phrases, balance between soloist and choir, sensitivity to the text, and its relative unfamiliarity to the choristers have made this piece a bit more challenging.

Q: Since this is your final Christmas concert, did you choose a particular piece that means a lot to you for the boys to perform?
A: Yes. “On This Day Earth Shall Ring” by Haldane Campbell Stewart [1868–1942]. Stewart was a renowned cricket player, in addition to his work as a choir trainer at Magdalene College, Oxford. I first heard this piece on an old recording of the Liverpool Cathedral Choir, which I’ve had for about 40 years. It’s one of my favorite Christmas choral pieces.

Q: What's your favorite piece of music from past Christmas concerts that you weren't able to perform this year?
A: Well, I’d have to say the Britten “Ceremony of Carols,” just because it is the quintessential boys’ Christmas work, renowned and loved throughout the world. We have performed it many times, the last time in 2015. We try not to repeat major works from year to year -- of course, the perennials such as “Tomorrow Shall be My Dancing Day” are always on the program!

Q: Any funny stories from past Christmas concerts?
A: Nothing in particular, but I will share this: We have a tradition of inviting alumni who are present to come up and sing the final pieces -- which do not vary from year to year -- with us. It’s usually the case that several fine young men come up to sing -- and I have no idea who they are, since I knew them, in most cases, as trebles!

Christopher Porter is a Library Technician and editor of Pulp. He also has two wiggly, rambunctious boys in the prep choir.

"A Boychoir Christmas" will be performed twice: Friday, December 9 at 7 p.m. at First Presbyterian Church of Ypsilanti, 300 N. Washington St.; Saturday, December 10 at 3 p.m., First Presbyterian Church of Ann Arbor, 1432 Washtenaw Ave. You can reserve tickets at aaboychoir.org/reserve.