In many old Warner Brothers cartoons, such as Bugs Bunny, the music and sounds in the background help to tell the story by adding a drum roll before a character gets hit in the head or simply by having the characters move their feet in time with the notes being played, the characters moving faster when the tempo increases. This music is usually not being created by anything in the animation so we must assume that the music is not really heard by the characters, despite the fact that they move in time with the music and act according to how dramatic the music is. Music adds to the cartoons by adding funny sounds to slap-stick jokes and by setting the appropriate mood music for what is going on in the cartoon. The flow of these cartoons wouldn't be the same with out music, or as entertaining.  The link at the end of this blog is of a cartoon from 1935 entitled "An Elephant Never Forgets".  This cartoon is completely governed by the music in the background, meaning every character who speaks sing along to the background music instead of talking normally and every action preformed by the characters in the animation will go along with the music as well.  The orchestral music and goofy sound effects going along with the animation in perfect harmony is what makes those old cartoons so interesting, memorable and classic. 

An Elephant Never Forgets