In music, a refrain has two parts: the lyrics of the song, and the melody. Sometimes refrains vary their words slightly when repeated; recognizability is given to the refrain by the fact that it is always sung to the same tune, and the rhymes, if present, are preserved despite the variations of the words. Such a refrain is featured in "The Star-Spangled Banner," which contains a refrain which is introduced by a different phrase in each verse, but which always ends: