Creating innovative interactive multimedia presentations requires a great deal of time, skill, and effort. We have developed a multimedia synchronization toolkit, called Nsync (pronounced 'in-sync'), to address the complicated issues inherent in designing flexible, interactive multimedia presentations. The toolkit consists of two major components, a declarative synchronization definition language and a run-time presentation management system. The synchronization definition language supports the specification of synchronous interaction, asynchronous interaction, and fine-grained relationships among multiple media objects. The language also supports the combination of interactive behavior and fine-grained relationships through the use of conjunctive and disjunctive operators. We illustrate the use of the language through several examples. We argue that with the inclusion of asynchronous interaction, pre-computed playout schedules are too inflexible, thus we have developed a new presentat...