Grammy Award winner Gwen Stefani will join the previously announced Pharrell Williams as a coach on the upcoming seventh season of the singing competition "The Voice." NBC said Tuesday that Stefani, a multiplatinum singer both solo and with her band No Doubt, and fellow Grammy-winner Williams will each perform a song on Monday's live show. "The Voice" executive producer Mark Burnett tweeted his congratulations, saying "Welcome to 'The Voice' family!" Stefani herself tweeted, "It's true!"