Every year on Halloween night, thousands of exuberant Yalies pack into Woolsey Hall to be entertained by nearly 100 classical musicians. But the Yale Symphony Orchestra’s annual Halloween show is much more than a concert.

The YSO Halloween movie and its accompanying live soundtrack have developed during the past two decades into a firmly established Yale tradition that is as eagerly anticipated as any other social event at the University. This year’s show is the culmination of a year’s worth of planning, producing and practicing — and Yale students don’t know the half of it.

“Every year the tradition is to parody a big movie and spoof on-campus life at Yale, so we try to include as many jokes as possible,” Ethan Green ’07, the director of this year’s film, said.

Batman, Indiana Jones and Kill Bill are among the movies parodied in the past.

As in prior years, the movie itself is completely silent and its action will be complemented by the onstage orchestra playing selections that range from classical favorites to popular hits and familiar themes from TV shows and movie soundtracks.

“You start planning the Halloween movie on November first the year before,” Lisa Schilling ’06, who starred in last year’s film, said.

This year’s production was no exception. After the initial brainstorming last November, a committee of individuals met this past May to organize and begin considering proposals, Green said.

“April and May is when we got serious,” Green said. “We got together and put forward ideas of what we wanted to accomplish so that when we came back this fall we really knew what we wanted to do.”

Those ideas continued to evolve throughout the summer, as committee members communicated by e-mail to perfect and refine the existing concept, YSO president Bill Perdue ’07 said. A committee of a dozen people met during Camp Yale to make final decisions regarding director, actors and plot, he said.

Filmed around campus, the movie traditionally employs one major motion picture as its predominant theme, which remains a closely-guarded secret until the night of the performance.

“Based on some recent events in the Ivies, people will really appreciate the motivation of the characters, which makes it even funnier,” said Jennifer Shields ’06, who will play the romantic lead in this year’s movie. “Everyone will get and love this theme. The crowd will go wild when they see it.”

After a few more meetings in early September, movie shooting started and the finale itself was filmed as recently as two Sundays ago, although the production is not yet complete.

David DeAngelis ’08, who stars as the hero in this year’s movie, said he was approached only two days before classes began and asked to play the lead role.

“We started the second week in September and we’re still filming,” DeAngelis said. “I had no idea how many hours of effort went into it. It’s a question of chipping away at the project one piece at a time.”

David Einstein ’07, who plays the villain in this year’s movie, said perfecting body language and physical action is critical to a silent film, which justifies the hours of filming required to obtain just a few minutes footage.

Audiences can expect certain traditions of the YSO Halloween show to continue. This year’s movie features the familiar live scenes, where the movie pauses and characters come out onstage to do a dialogue. Regarding the annual surprise guest from the faculty or administration, Shields said this year’s actor occupies a substantial role.

“It’s too bad it’s a silent movie, because the things this person was saying during filming were hilarious,” Shields said.

As soon as material is filmed, it goes to the computer lab for editing, which accounts for the bulk of production time, Schilling said.

Einstein said last year’s finale was interesting, but was not worth the several days of filming it required and consumed a disproportionate amount of producers’ efforts. Crediting Green as the engineer of this year’s special effects, Einstein said this year’s movie includes simple effects that are still aesthetically impressive.

Last Thursday, five or six YSO members sat down to view a rough cut of the movie for the first time and choose musical selections for the soundtrack. Conductor Nicholas Chong ’07 said that since the movie isn’t finished until late in the process, many of their decisions are restricted by what music the orchestra can obtain and learn in a short period of time.

“We have our own YSO library and access to the library at the Graduate School of Music, but our choice of music for a Halloween show is still necessarily limited,” Chong said. “Certain old favorites we try to keep in because people like them, but this year’s score is definitely still appropriate to the theme.”

“It’s a question of matching,” Perdue said. “We have to ask ourselves, are we looking for something declaratory here? Something spooky? Something romantic?”

The orchestra learns the score in less than a week, attending three rehearsals lasting two and a half hours each. This schedule is a challenge for the musicians, who work on the Halloween show in the middle of their regular concert season, said Chong.

At the orchestra’s first rehearsal for the Halloween show, Purdue stressed the tradition and significance of the performance.

“As an event, this is on the order of the Harvard-Yale game or Spring Fling,” Perdue said. “It’s bigger than Spring Fling.”

Perhaps that enthusiasm is what generates the same anticipation among students attending the show.

“Last year, director Bill Strom did such a fabulous job,” said Sarah Cannon ’06, who cited the surprise guest as her favorite part of that program. “He had Dean Salovey dressed up as a schoolgirl, and people raved about it. Bill’s movie will definitely be a tough act to follow.”

If their excitement is any indication, this year’s YSO is up to the challenge. Cellist Dan Lewis ’09 said he is looking forward to the Halloween show, which is generally the orchestra’s biggest performance of the year.

“I’m very excited about it because I’ve heard it’s an incredible amount of fun,” Lewis said.

Perdue said he anticipates that the show will meet, if not exceed, expectations on both sides of the stage.

“It’s a night when the orchestra gets to look across the stage and feel like a rock star, and that’s a big deal for classical musicians,” he said. “We’re used to respectful, golf-clapping crowds, not screaming fans. This performance is the most fun we will ever have with our instruments.”