This paper discusses reduplication as a technique of word formation in German. In contrast to previous approaches, which consider reduplication as extra-grammatical and unproductive, this study identifies rhyme and ablaut reduplication as truly reduplicative processes in the morphology of German. A sizeable corpus of these reduplications and an acceptability rating study attest the productivity of this phenomenon. Other contemplable cases of reduplicative structures are properly treated as either phonological doubling, lexical sequencing, or (special cases of) compounding. An analysis in terms of Optimality Theory (OT) is offered which suggests that both rhyme and ablaut reduplication emerge when a segmentally and prosodically underspecified expressive morpheme is attached to a base – given that the base strictly obeys certain word prosodic requirements. The present approach considers the morphophonology to be blind to morphosyntactic structure and consequently eschews constraints that make explicit reference to base-reduplicant correspondence. The OT grammar successfully models the emergence of the fixed bipedal structure, the obligatory segmental deviance of the reduplicant, non-exponence of the expressive morpheme in the case of non-trochaic bases, the variable linearization of base and reduplicant in ablaut reduplication, and the interaction of reduplication with segmental alternations. Certain (crosslinguistic) correlations regarding constraints on reduplicative word formation and poetic devices, such as rhyme and meter, are discussed.