It's filmed in front of a live studio audience so the laughing you hear is the audience. However, the more times the actors mess up their lines and scenes, it becomes less funny to the audience so they add more laughter during editing of the episode.
They record the audience laughter during taping.
But then in the editing process they use that recorded laughter to build a laugh track. It's called sweetening...basically manipulation. They turn it up, down, or insert it where they wish.
As for the lyrics...a poorly written time line embedded in a musically annoying song does not suffice. The package is dumbed down for the typical television viewer....daddy-o!