As if a day could go by without a musical reality competition making an announcement about celebrity judges. NBC announced Monday that Usher and Shakira will replace Cee Lo Green and Christina Aguilera on Season 4 of The Voice, to air this spring. (Season 3 got underway earlier this month.) Current judges Adam Levine and Blake Shelton will return for the fourth cycle. “I am a singer and performer first, and I am so excited to get back to that love,” Aguilera said, adding that the back-to-back seasons is too much of a commitment for her. Green also has new music in the works, as well as an NBC comedy based on his life.