OVERTURE:
The overture is the introductory musical piece played before a musical which contains many of the musical motifs and themes of the score.
MARK:
The mark is the place on stage where an actor is to deliver a particular line or carry out some action.
VAUDEVILLE:
Vaudeville is the form of show consisting of mixed specialty acts, including song, dance, acrobatics, comic skits and dramatic monologues.
INTERLUDE:
From the Latin interludium (between the play), the term refers to a short dramatic sketch in early English drama. The short, light pieces would be performed between the acts of more serious plays.
LIBRETTO:
The narrative dialogue or spoken part of a musical play, as opposed to the lyrics and the music.