The use of integrated time-signature changes in eighteenth-century music has received little attention, probably because it is not considered a significant part of an eighteenth-century composer's toolkit. If mixed metre is discussed at all, it is linked with the late eighteenth-century conceptual shifts in metric theory brought about by Johann Philipp Kirnberger's circle. There exists, however, a substantial repertory of mixed-metre pieces from the first two thirds of the eighteenth century, with many examples to be found in the works of Georg Philipp Telemann. This repertory destabilizes any direct connection between mixed metre and the so-called Akzenttheorie, reminding us that the relationship between theory and practice at this time was far from straightforward. Beyond setting out how early eighteenth-century mixed metre operated within and against contemporary understandings of musical time, this article explores aspects of the origins, function and performance of these remarkable pieces.