Duncan Sheik, who died at 56, lived two distinct artistic lives — one brief and bright in the pop charts of 1996, and one deeper and more enduring on the Broadway stage. Where many artists cling to the identity that first brought them fame, Sheik quietly released it, trading the machinery of commercial pop for the compositional freedom of musical theater. His Tony Award-winning score for 'Spring Awakening' became the proof that the harder path had been the truer one.