When S.E. Gross Middle School band director Katie Pilson chose Michael Colgrass' "Old Churches" to be part of the annual winter concert, she didn't realize just how apt the choice was.

She knew that Colgrass, who won the Pulitzer Prize for Music in 1978, was a former Brookfield resident. What she didn't know was that Colgrass was an S.E. Gross School graduate, as well.

"I actually learned about the piece in a class I took at Northwestern over the summer a few years ago," said Pilson, who has been band director in District 95 for six years. "Until I looked into it, I didn't know he was a graduate of District 95."

In fact, Colgrass visited his alma mater last spring during a trip into town from his home in Toronto, Canada, and spoke with Pilson about the piece that seventh- and eighth-grade students in the Gross School symphonic band will be performing during their concert tonight, Dec. 9, at 7 p.m. in the school's auditorium.

"He wrote it for a student ensemble," Pilson said. "It was specifically written so students in younger groups could explore some of these techniques."

Those "techniques" include improvisation, something school bands don't typically traffic in.

"This one is very slow and very exposed as far as the music goes," Pilson said. "Students are responsible for their own parts and really have to listen."

Colgrass wrote "Old Churches" in 2000. In an e-mail to the Landmark last week, Colgrass said that the piece was "a commission from the American Composers Forum in Minneapolis through their program called Bandquest, intended to raise the standards of music for middle school children by commissioning professional composers. I was one of 15 chosen for the task."

While the piece sounds advanced harmonically, combining Gregorian chant and improvised sounds that create the impression of sounds echoing within an old church, Colgrass said the principles he used were basic ones.

"The improvisatory aspects of the piece are very simple," Colgrass said. "I derived them from listening to the children warming up on their instruments, where they would freely play things no one had written but that they are obviously capable of doing.

"I just devised a notation to represent these free-flowing gestures they make running their fingers over their instruments. My goal was to achieve a certain musical result, but also to open a door for them to the whole idea of improvising, something not normally taught."

Pilson said another challenge of the 5-minute long piece is that it's not all written in the same time signature.

"There's some free time in there, so it's different every time we rehearse," Pilson said.

"We can't rehearse it for long periods of time, because it's pretty serious music. The attention span is not what a high school or college student would be."

Of the 43 students in the symphonic band about half get the chance to solo improvisationally. The piece also calls for aluminum bowls to be used for improvised percussion.

"Aluminum kitchen salad bowls - the large ones - ring nicely, so I got the idea of suspending them and hitting them with a soft-edged stick," said Colgrass. "They are very suggestive, sounding to some like muffled church chimes in the distance, or ... like footfalls in a cathedral. At various times certain instruments play what I call the 'murmuring effect' where the kids play any notes they want, softly and as fast as possible to simulate voices murmuring in hallways a la prayer."

The symphonic band will also play the holiday classic "Do You Hear What I Hear," and the group is just part of show, which features five to six different performing groups from S.E. Gross School, including bands and choirs.