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."
- 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.