An audience will let you know if a song communicates. If you see them kind of falling asleep during the song, or if they clap at the end of a song, then they're telling you something about the song. But you can have a good song that doesn't communicate. Perhaps that isn't a song that you can sing to people; perhaps that's a song that you sing to yourself. And some songs are maybe for a small audience, and some songs are for a wide audience. But the audience will let you know pretty quickly.