When neither of those is able to do so ( or in rare cases where the telecast producers decide to go with someone else ) , the Academy chooses more well-known entertainers to perform the song at the ceremony . For example , Robin Williams performed " Blame Canada " from '' South Park : Bigger , Longer & Uncut '' at the 72nd Academy Awards instead of the film 's voice actors , Trey Parker and Mary Kay Bergman ( Bergman died a few months before the show ) . Beyoncé Knowles sang three nominated songs ( one of which was a duet with Josh Groban ) during the 77th Academy Awards even though she had not performed those songs in any of the respective films
77th Academy Awards
77th Academy Awards
Academy Award for Best Original Song