In days of yore, when most musicians were employed either by the church or royalty, composers supplied music plentifully for holidays and feasts – an arrangement that yielded, over the centuries, an enormous body of Christmas works, many of which remain in the canon. Now that those institutions are largely out of the business of keeping composers busy, production has dwindled, and though composers continue to create Christmas works, the new ones seem to come and go, without making much of a mark.

There was a moment, however, when it seemed that industry might pick up where the church and royalty left off. In 1951, near the dawn of the television era, NBC commissioned Gian Carlo Menotti – then 40, and a prolific and popular opera composer – to write a Christmas opera, to be broadcast live on Christmas Eve. It was a brilliant idea: The work Menotti produced, “Amahl and the Night Visitors,” quickly became a holiday staple, and it remains a beloved Christmas piece – at 65, the last large-scale work to become a holiday staple.

Portland concertgoers already had a glimpse of “Amahl” this season, when ChoralART included scenes in its “Christmas at the Cathedral” concert. On Friday evening (with a repeat on Saturday), Williston-Immanuel United Church presented the full work, in a simple but effective production, staged and conducted by Kathleen Scott, the church’s director of music, with a cast that combined professional and amateur performers.

Menotti had a fascination with the sentimental side of faith and mysticism (you hear it in “The Medium” and “The Saint of Bleecker Street,” as well), but also a gift for melody and a virtually unerring sense of what works on the stage. “Amahl,” inspired by a Hieronymous Bosch painting, “The Adoration of the Kings,” is a fantasy about an impoverished, disabled young boy and his mother, at whose home the three kings stop to rest, on their way to visit the infant Jesus. When Amahl offers his crutch as a gift for the child, he is miraculously cured, and joins the kings on their journey.

Menotti insisted that the title role be sung by a young boy, a decision that gives Amahl a natural innocence, as well as a measure of unpredictability. Scott cast different singers as Amahl and the Mother each night, and on Friday, the title role was sung by Alex Ecker, a seventh grader at Cape Elizabeth Middle School, with some summer camp acting experience on his resume.

Ecker handled the job ably, bringing a touch of precociously understated humor to his interactions with both his mother and the kings. If he hasn’t yet worked out how to make a smooth transition from his aptly theatrical chest voice to his lightly floating falsetto, how many seventh-graders can? Menotti’s original Amahls were highly trained by sopranos, but he undoubtedly knew that this would not always be the case, and indeed, hearing a young singer grapple with the wide-ranging line Menotti provided is part of the work’s charm.

Danielle Vayenas sang the Mother’s music with beauty and suppleness, avoiding the temptation to sound overwrought, even when expressing her frustration with Amahl’s tendency to fib (she doesn’t believe his reports of an exceptionally bright star, or of the three kings at the door), or in the scene where she is caught stealing some of the kings’ gold.

The kings – George Aud as Kaspar, Scott Wheatley as Melchior and Peter Lightfoot as Balthazar – made strong vocal contributions, both as an ensemble and individually, and Lightfoot handled Balthazar’s comic turns with an irresistible sparkle. Kasey Gabloff, a 16-year old dancer, offered an elegant turn in the small space available on what was by then a crowded stage (besides Amahl, his mother and the kings, a shepherd’s chorus had turned up), and Nick Sutton filled out the cast as the kings’ page.

Scott’s staging was simple and direct, with a backdrop of glowing stars (including, of course, the Christmas star) and a few simple pieces of furniture. More importantly, she had a fine chamber ensemble at her disposal, which gave a warm, polished performance, within which Aaron Emerson’s shapely account of the prominent oboe line was particularly notable.

Allan Kozinn is a former music critic and culture writer for The New York Times who lives in Portland. He can be contacted at allankozinn@gmail.com or on Twitter @kozinn.