Synchronization of multiple media is a major issue in multimedia applications; in distributed systems, this problem is aggravated further. We present tools for the creation, editing, and presentation of synchronized multimedia objects. In particular, we describe a graphical Synchronization Editor for the specification of synchronization schemes and a Synchronizer for the execution of multimedia presentations. We emphasize the requirements imposed by an underlying distributed heterogeneaus environment, as weff as support for interactive user control. The tools described are not restricted to a fixed set of media, but support the incfusion of arbitrary user-defined media. The Synchronization Editor and Synchronizer are part of the Mode project, which in turn covers the 'distributed multimedia object support' part of NESTOR, an authoring//earning environment deve/oped jointly by the Universities of Karlsruhe and Kaiserslautern and the Digital Equipment CEC, Karlsruh