Theme

In music, themes are frequently called motifs. After the principal theme or motif is announced, a second voice takes up the second melody, called a countertheme or countermotif. In a three-part fugue, the principal theme is announced three times in three different voices -- soprano, alto, bass -- or some variation of that. In a four-part fugue, the principal motif is announced four times. A leitmotif is a theme associated with a particular character in a play.