Listen: Tegan and Sara's 'Shudder to Think'

"I've been very excited about Dallas Buyers Club ever since hearing about the film," Sara Quin tells Rolling Stone, where she and her sister Sara premiered their new track, "Shudder to Think." "With the soundtrack supporting such an important cause, we're very excited to contribute a previously unreleased b-side to the campaign."

The song, "Shudder to Think," is on the soundtrack for the film, which is out Nov. 1, and stars Matthew McConaughey and Jared Leto. Dallas Buyers Club tells the story of how one homophobic straight man, when he's told he has AIDS and 30 days to live, develops a concontroversial system for AIDS and HIV patients to buy and receive alternative drugs and treatments--and his path to greater empathy for those around him.

Other artists contributing to the soundtrack, out Oct. 29, include Thirty Seconds to Mars (Leto's band, for which he's lead vocalist, guitarist, and songwriter), My Morning Jacket, Manchester Orchestra, Neon Trees, Fitz and the Tantrums, Portugal. The Man, Cold War Kids, Capital Cities, AWOLNATION, The Naked and the Famous, The Airborne Toxic Event and Blondfire.

Listen to Tegan and Sara's track below: