GREENWICH — The melody bounces from highs to lows like a swing oscillating from one end to the other, swaying seamlessly in the wind without ever quite reaching a peak.

An easy rhythm sounds a little like birds fluttering, and as choristers repeat a two-syllable “cuckoo” over and over, listeners can almost imagine one of Mary Poppins’ favorite robins emerging from a nest to stretch its wings after a cold British winter.

And yet “Sumer Is Icumen In” far predates Disney’s 1964 classic, and in some ways paved the way for its creation. As one of the first secular pieces of vocal music, and the oldest known song to incorporate six-part polyphony, the 13th-century English rota symbolizes a revolutionary moment in musical development.

But if during the Medieval Era the rota meant radical change, its airy tune hardly holds much gravity. Nor is it worse for the ware of age — choristers today can pull it out for a jaunt, and it still sounds fresh and breezy.

Perhaps that is why Paul F. Mueller, the Greenwich Choral Society’s music director, has chosen to open his group’s program for Curiosity Concerts with “Sumer Is Icumen In.” It seems nearly perfect for a child — mysterious, complex and, maybe most importantly, brief.

“We’re trying to nurture future singers and audiences, and we want young people to know that there is this kind of music,” said Susan Ellis, a 39-year member of GCS and its vice president of marketing.

At 3 p.m. Sunday, Curiosity Concerts in conjunction with the Ashforth Children’s Concert Series will feature GCS during its fifth show of the season in Cole Auditorium at Greenwich Library. Tickets are free but require preregistration online at

This is not the vocal group’s first time collaborating with the family concert series — back in January 2015, members performed excerpts from the comic opera “H.M.S. Pinafore.”

“We’ve had a few ensembles back, but it's the exception and definitely not the rule. So it has to be pretty extraordinary,” said Shelly Cryer, Curiosity Concerts’ producer.

When GCS had its first appearance with the series, the venue was packed, with a long waitlist of others who wanted to attend and one of the lowest no-show rates for any of the concerts, she said.

This time, Mueller has decided to take the one-hour program in a different direction. Starting with “Sumer Is Icumen In,” he has curated a bill that surveys choral music all the way into modernity, with different sounds and intentions.

“It’s a little tour through choral repertoire, I think, and so it’s a revue and a musical journey,” Cryer said.

“It’s not only different eras, but it’s also different types of music,” added Ellis.

One of the songs is literally the imitation of the sounds snow makes as it falls. Another is a jazzy Gershwin number.

Yet another is “Geographical Fugue,” a piece that uses opportunely named cities, states and countries to construct a strict contrapuntal form.

“It just shows you what you can do with the human voice and a few words that have interesting rhythms to them,” Ellis said.

Though GCS’ members number in the hundreds, Sunday’s performance will feature a smaller group of just over 20 singers to fit on the Cole Auditorium stage. But even if the ensemble may be less expansive than usual, they will be no less impressive, Cryer said.

“I think that part of what we try to do with these concerts is offer a true concert experience but also an intimate one, and you absolutely can get the beauty and full effect of a chorus without having the full roster of singers,” she said.

She remembered the group’s last stint with Curiosity Concerts as a case in point.

“It felt extraordinarily robust,” she said. “The sound was breathtakingly rich and superb.”

Cryer positioned the matinee as an opportunity for parents and grandparents who are fans of GCS to introduce the children in their lives to the group.

“These are all great pieces, and if anybody really cares, they can learn a lot about music history (from) this program,” Ellis said.