You may have heard Curtis Harding 's voice before, perhaps without realizing it. That's because, for a number of years, he worked with a familiar Atlanta native: CeeLo Green. Harding sang back-up vocals for CeeLo and even co-wrote songs with the Grammy Award-winning musician, like "Grand Canyon" — which was a bonus track on CeeLo's 2010 album, The Lady Killer . After that and several other collaborations, Harding launched his solo career, applying his distinctive falsetto vocals to his own style