Leitmotif

n.	1.	(Mus.) a guiding theme; in Wagnerian opera, a marked melodic phrase or short musical passage which always accompanies the reappearance of a certain person, situation, abstract idea, or allusion in the course of the play; a sort of musical label. Also called Leading motive.
	2.	a recurring theme in the activities of a person or group.

Noun

1.

leitmotif - a melodic phrase that accompanies the reappearance of a person or situation (as in Wagner's operas) Synonyms: leitmotiv

air, leitmotiv, line, melodic line, melodic phrase, melody, strain, tune