Opéra-ballet was a popular genre of FrenchBaroqueopera, "that grew out of the ballets à entrées of the early seventeenth century". It differed from the more elevated tragédie en musique as practised by Jean-Baptiste Lully in several ways. It contained more dance music than the tragédie and the plots were not necessarily derived from Classical mythology and even allowed for the comic elements which Lully had excluded from the tragédie en musique after Thésée (1675). The opéra-ballet consisted of a prologue followed by a number of self-contained acts (also known as entrées), often loosely grouped round a single theme. The individual acts could also be performed independently, in which case they were known as actes de ballet.