The last musical shoe has dropped with the Academy's announcement that Karen O will perform her Oscar-nominated track “The Moon Song,” from the Spike Jonze film “Her,” during the awards ceremony. The other Oscar nominees for best original song, whose appearances have already been confirmed, include Pharrell Williams (“Happy,” from the animated film “Despicable Me”), U2 (“Ordinary Love,” from the bio-pic “Mandela: Long Walk to Freedom”) and Idina Menzel (“Let It Go,” from Disney's animated fairy-tale “Frozen”).