Stylistically, rescue opera was an outgrowth of the "opéra comique", a bourgeois genre. Like "opéras comiques", rescue operas contained spoken dialogue, popular musical idioms, and bourgeois characters. Works with libretti by Michel-Jean Sedaine were particularly influential. The influx of suspenseful or tragic subjects into "opéra comique" caused confusion in a system where tragedy was associated with through-composed scores and comedy with dialogue, precipitating a shift of musical theatre genres that paralleled the political shift which empowered the middle-class. Carl Dahlhaus writes, "No longer did the bourgeoisie function in comic casts merely as the butt of jokes; it demanded, and received, its part in the dignity of tragedy."