Extras exist in the background of a movie scene - sitting, maybe, or walking by.

In some cases, though, particular talents are required.

For the Dustin Hoffman drama "Boychoir," which filmed a few days in New Haven, that meant being a trained musician.

In the movie, a troubled 11-year-old attends a boy choir school, where he runs afoul of a demanding choir master.

For a scene where the main character sings his first major solo, "Boychoir" needed people to pretend to be the orchestra accompanying him.

Where to find actual musicians? A production person who had previously worked with Colchester Civic Orchestra members on the indie short "M Is For Maestro" contacted them about this new film, according to orchestra president Lisa Peeling, of Marlborough.

The orchestra emailed other area ensembles to seek musicians to fill out the numbers that "Boychoir" wanted. They recruited folks from the Willimantic and Manchester groups - as well as Emily Clark of East Lyme, who plays with the New London Community Orchestra.

On March 15, the 20 musicians all traveled to Woolsey Hall on the Yale University campus for a day of filming.

They took their places onstage, and the filmmakers asked the orchestra members to hold up their instruments to see their playing positions - and to make sure they could get the shot they wanted. They proceeded to shoot the same scene from a variety of angles.

The instrumentalists weren't meant to actually make music. Their task was to mime playing instruments to a previously recorded track of two pieces, both by Handel: "Coronation Anthem from Zadok the Priest" and "Ode for the Birthday of Queen Anne."

But, Clark says, "especially on a string instrument, it's very hard to do that without making any sound. So we were playing softly."

Part of the movie's faux orchestra, too, was Andrew Raibeck, of Salem, who is a clarinetist with the Colchester orchestra. The pieces the "Boychoir" orchestra was playing didn't call for a clarinet, though. So Raibeck borrowed a trumpet from a friend and, calling upon his time playing the alto horn in high school, he was able to convincingly pretend to play the trumpet.

As for brushes with Dustin Hoffman, yes, a few of the musicians could lay claim to that. Raibeck says that, at one point, the camera was placed between two trumpet players, to get the instruments at a certain angle. Someone standing behind Raibeck whispered to him, "Can you raise your trumpet a little higher?" Raibeck didn't realize it then but heard from people later that the whisperer was, in fact, Hoffman.

Hoffman was certainly a friendly presence. Peeling, who plays the cello, says the actor chatted with a couple of the Colchester oboists about dogs. He told Peeling she should Google a video of a cell phone going off during a concert and prompting the star violist to play the cell ring on his instrument.

The film - directed by Francois Girard, whose previous works include "The Red Violin" and "Thirty Two Short Films About Glenn Gould" - also stars Kathy Bates and Debra Winger, who were not on set, and Josh Lucas, who was there for one scene.

While the instrumentalists were busy as orchestra members, some of their significant others came to the set, too, and became extras portraying concert-goers - including Jackie Raibeck, who is Andrew's wife, and Justin Scace, who is Clark's boyfriend.

Since there weren't enough extras playing audience members to fill Woolsey Hall, the moviemakers kept shifting them and shooting them in different areas of the auditorium. They were led through sequences where they acted just as a real audience would: making conversation before the show, applauding, giving a standing ovation. With a little post-production work - though it's not clear if that means editing or digital effects - it should look like a full hall.

The wardrobe person, meanwhile, made sure the extras' outfits fit in with the movie's vision; she asked Scace, of East Lyme, for instance, to change his paisley tie for a diagonally striped one he also brought, to wear with his navy pinstripe suit.

The women were told to wear cocktail dresses in jewel tones but not in black or white, Jackie Raibeck recalls. Raibeck wore an emerald dress and consequently wasn't seated near the other women in emerald, to keep colors balanced onscreen.

It was a long day, with musicians putting in 10 ½ hours, and the audience extras going two hours beyond that.

Clark says, "I was really struck by how meticulous they are with everything, from the framing to the lighting, and how long it takes to film. It was all day to film something that'll be probably at most five minutes in the movie."