LOS ANGELES, Sept. 19 -- Duncan Sheik, the singer-songwriter who turned one of the defining soft-rock hits of the 1990s into an unlikely second act as the Tony-winning composer of Spring Awakening, has died. He was 56.

Sheik died Thursday from organ failure, his mother Suzanne Sheik told The New York Times, according to the Associated Press.

For casual listeners, Sheik remained synonymous with Barely Breathing, the quietly insistent single from his 1996 self-titled debut that spent 55 weeks on the Billboard Hot 100, peaking at No. 16 and earning him a Grammy nomination.

But his most enduring impact may have come a decade later, when a musician who considered himself a Broadway outsider helped blow open the sound of the American musical...