He first uses his clarinet as a full scale attack on Burger-Beard, who resists the loud music. Later, during the chase, he uses it in a last-ditch attempt to keep the book away from Burger-Beard before collapsing in exhaustion.
He does not appear until after Plank-Ton saves the gang and retrieves the formula. Squidward wishes to stay in this form forever, but SpongeBob returns everything to normal via the Magic Book, although allowing Squidward to keep his "rock-hard abs."
Sour Note can summon a clarinet that is able to play really loud music.
Unlike actual Squidward, Sour Note only has two feet instead of four.