 The subject matter was generally far less elevated too; 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".