Although Kern's songs are easy to remember after hearing a few times, they are not simple. His melodies -- the musical line of the song -- are always inventive, even demanding. An example of his inventiveness is the song "All the Things You Are". Several composers say they consider it the greatest song ever written. Singers continue to like Kern songs because they can be sung in many different ways. The melody remains the same. But different singers can change the feeling of the song completely.