<Li> Matthew McConaughey as Buster Moon, an optimistic koala who plans to save his theater from closure by holding a singing competition . </Li> <Li> Reese Witherspoon as Rosita, a pig who gave up her teenage music dreams to become a devoted wife to Norman, and mother to their 25 piglets . </Li> <Li> Seth MacFarlane as Mike, an arrogant street musician mouse with a big Frank Sinatra-esque voice . </Li> <Li> Scarlett Johansson as Ash, a teenage porcupine punk rocker who takes part in an alternative - rock music duo with her boyfriend Lance . </Li>

Who does the singing for mike in sing