Drugs, depression and disease may not be the first themes that spring to mind when imagining what happens behind the scenes of a real-life 'glee club.' But a new documentary that follows two Toronto high school show choirs found students are battling their demons through song.

'Unsung: Behind the Glee' follows two rival Toronto high school glee clubs-- from Etobicoke School of the Arts and Wexford Collegiate School for the Arts -- as they prepare for the annual Show Choir Canadian National Championship.

Jacob Madonia, 18, told CTV's Canada AM he was depressed and abusing drugs when he joined the show choir at Etobicoke School of the Arts.

In an interview Wednesday, he said being part of the glee club "really drove me to want to better myself." The group helped him face his issues and move past his depression.

"I had this amazing support system of about 40 people who felt like a second family to me… Not only did the art and the singing and the performing help, but the choir itself really helped to better me as a person."

Madi Scott, 16, from Etobicoke School of the Arts, was diagnosed with cancer when she was a child. Chemo made her vocal chords swell and she was told she'd never sing again. For her, show choir has been a pivotal experience in her life.

"It was SickKids that saved my life, but it was performing that gave it back to me," she told Canada AM.

"It was that performing that drove me to get out of bed, and it was that performing that made me want to get out of the hospital and made me want to just go back to doing what I love."

Another student, Dean Deffett, commutes over an hour to attend Wexford Collegiate. He left his old school because he was bullied. "I remember they were just dragging me across the field," he said in the documentary.

He never told anyone about his experiences before switching schools: "I guess the biggest part of bullying is that you're embarrassed by it. You feel like you've done something."

"It's really about the power of art to change lives, to heal," director Moze Mossanen told Canada AM about the documentary, which airs on Dec. 4 at 9 p.m. ET on TVO and TVO's Doc Studio.

"It was a labour of love," Mossanen said. "Sometimes you make a film that you connect emotionally with, and for me this was one of those films."