Parts of downtown were without power throughout the afternoon and evening due to trees and tree limbs falling on power lines and poles, according to a Duke Energy representative. Almost 300 customers in the Bloomington area were without power, some until early Monday morning, due to the need to move fallen branches before making repairs.

Guillen, as well as the other musicians, BSO staff and board members and the Buskirk-Chumley Theater staff needed a plan. An idea found its way backstage, where Guillen still waited in the dressing room: What about using cellphones for light?

“I didn’t even think twice,” Guillen said. “I was really worried about the audience waiting. We didn’t know how long it was going to take to fix the power, and people might have to go home. The air conditioner was off. It was dark in there, and people might have felt unsafe in the dark.”

When he heard that there were still patrons who hadn’t purchased their tickets in advance showing up for the concert, he said, “it wasn’t a question of whether to make it work, but how to make it work.” The concert wouldn’t be canceled or rescheduled, and wouldn’t be delayed any longer than it had to be.

Selling tickets would be difficult — there was no power for credit cards, and some people didn’t have cash. Guillen said some audience members were let in for free, and several ended up making donations, “some even more than the ticket was worth.”

Conditions weren’t ideal, quick decisions had to be made and the show ran a little late.

“When people are willing to put up with some inconveniences and circumstances that are not ideal, it’s really inspiring,” said Molly Brush, a cellist in the orchestra. “We wanted to do our best for everyone who had come out to see us.”

Because the full orchestra wouldn’t be on stage for the opening number, some members were sitting in the balcony when the power went out. Instead of sitting back and relaxing during the opening number, or preparing for their own parts later, they headed to the stage with their cellphones.

Brush said she was able to see her music thanks to the light of clarinetist Carl Weinberg’s flashlight app.

“He just kind of crouched behind me the whole time,” she said.

Guillen said it made him think of how the piece might have been originally performed in Mozart’s time: by candlelight.

“And here we were with cellphones,” he said.

In the audience, Sue Swaney, director of the Voces Novae chamber choir — of which Guillen is a member — was nervous for her colleague. She was afraid the problems leading up to his opening solo would be similar to an athlete being “iced,” when a timeout is called right before a play to divert the player’s focus.

“He was ready to go out and play a concerto, and all of a sudden he had to solve all of these problems,” she said. “But he walked out there and gave a beautiful speech, and played that concerto very beautifully.”

Despite the initial obstacle, Brush said, the players found some benefits from their dark situation.

“Playing in these difficult circumstances, without a lot of our normal visual cues, I think we were listening better and just being more alert and aware of each other.”

Intermission came after the Mozart piece, which would be followed by a new challenge. The venue was still dark, and Duke Energy was estimating power would be back by 1 a.m. A full orchestra would be needed on stage for the remainder of the performance. The next piece would be a local premiere of music composed by Leigha Amick, a student at the Indiana University Jacobs School of Music.

“There was a sense from the orchestra that they were game,” Swaney said. “They just wanted to play.”

With 40 minutes of music left in the program, Guillen announced that they would make a decision shortly after 8 p.m. as to whether the show would go on.

“At that point, we were wondering, ‘Is the power going to come back on anytime soon?’” Brush said. “’Are people really going to stick around and sit in the dark in what was getting pretty warm without the air conditioner?’”

Yes, they really were.

Without fellow musicians to light up the music and the conductor, the orchestra quickly used gaffer tape and whatever else they could find to rig their cellphones to light their music.

“Somebody went to the very back of the stage with a flashlight to illuminate my face and body so the orchestra could see me,” Guillen said.

Despite still not having all of the resources needed to host a concert, the orchestra continued with Modest Mussorgsky’s “Pictures at an Exhibition.” By this point, the men in the orchestra had removed their coats in the hot, muggy theater. The audience wasn’t giving up.

“I told the audience, ‘We’re going to do this,’” and everybody cheered,” Guillen said. “At that moment, boom! There was a little flicker. Everyone gasped.” The stage was still dark, but the house lights came on, and the air conditioner, too.

By the final piece of the Mussorgsky suite, the stage lights had kicked in.

“It was such a community experience and just amazing to feel the support of everyone, to feel that everyone wanted us to do it,” Guillen said. “We just kept asking, ‘Hey, don’t give up on us.’”

Brush said she didn’t hear anyone complaining or suggesting they cancel and go home.

“Everyone was just like, ‘How can we make this happen?’” she said.

Only cellphone footage of the performance exists, as Community Access Television Services had no power to record. Swaney, who attended the concert — the last in the orchestra’s 49th season — with her husband, said it’s one they’ll never forget.