Tegan and Sara revive 1980s-style pop on "Shudder to Think," which appears on the soundtrack The Dallas Buyers Club. The Canadian sisters combine dreamy synths with reflective lyrics on the effervescent track, musing on the chances not taken and the prospect of a life without someone special.

"I've been very excited about Dallas Buyers Club ever since hearing about the film," says Sara Quin. "With the soundtrack supporting such an important cause, we're very excited to contribute a previously unreleased b-side to the campaign."

The Dallas Buyers Club stars Matthew McConaughey as Ron Woodroof, a Texas man who died from an AIDS-related illness in 1992. Denied antiretroviral treatment after his diagnosis, he travels to Mexico to obtain black market medicine that he smuggles back and sells to other patients. Jared Leto also stars in the film, playing a transgender woman named Rayon with HIV who helps Woodroof operate his illicit business. Both McConaughey and Leto underwent dramatic physical transformations for their roles in the film, which opens November 1st.