Every night a new song is added to his repertoire. Key collects them all, and recounts them for the world. He tells the tales of everyone he meets and learns about. He sings to the crowd, for he lives through them. Without his audience, he would have no voice.
So he plays on for everyone. He gathers the tales of those he sees and meets, and shares them with his fellow mates. All of them have a laugh, and that is the way things are, and have always been, at Fou's Bar.