Rihanna will be joining the the crew on the ninth season of The Voice which will premiere on September 21 as a special adviser to the coaches;Gwen Stefani,Blake Shelton, Adam Levine, and Pharrell Williams. On Thursday,NBC entertainment chairman Bob Greenblatt announced that the 27-year-old hit maker will be assisting Blake Shelton, Adam Levine, Gwen Stefani and Pharrell Williams on the shows ‘ The Voice’ ninth season.