In music, a theme is the initial or primary melody. After the principal theme is announced, a second melody, sometimes called a countertheme or secondary theme, may play. 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 motif is a short melodic figure used repeatedly which may be used to construct a theme. A leitmotif is a motif or theme associated with a person, place, or idea. See also figure and cell.

Thematic changes and processes are often structurally important, and theorists such as Rudolph Reti have created analysis from a purely thematic perspective. Fred Lerdahl describes thematic relations "associational " and thus outside his cognitive based generative theory's scope of analysis.

Music without themes, or without recognizable, repeating, and developing themes is called athematic. Examples include the pre-twelve tone or early atonal works of Arnold Schoenberg, Anton Webern, and Alban Berg. Schoenberg (1975): "intoxicated by the enthusiasm of having freed music from the shackles of tonality, I had thought to find further liberty of expression. In fact...I believed that now music could renounce motivic features and remain coherent and comprehensible nevertheless."

The 1958 Encyclopédie Fasquelle defines a theme as follows:

• "Any element, motif, or small musical piece that has given rise to some variation becomes thereby a theme."

References

• Arnold Schoenberg (1975). "My Evolution", Style and Idea, p.88. Ed. Leonard Stein, trans. Leo Black. London.
• Nattiez, Jean-Jacques (1990). Music and Discourse: Toward a Semiology of Music (Musicologie générale et sémiologue, 1987). Translated by Carolyn Abbate (1990). ISBN 0691027145.
• (1958). Encyclopédie Fasquelle, cited in Nattiez 1990.