Wozzeck
Scene 3 (Invention on a Rhythm): People are dancing in a pub. Wozzeck enters, and when he sees Margret, he dances with her and pulls her onto his lap.  He insults her, and then asks her to sing him a song.  She sings, but then notices blood on his hand and elbow; everyone begins  to shout at him, and Wozzeck rushes out.