{\em Maestro} is a tool for managing sets of protocol stacks that satisfy varied quality of service or security requirements. Intended primarily for multimedia groupware settings, it permits a single application to efficiently operate over multiple side-by-side protocol stacks, each specialized to a different communication stream. Maestro can also be used to manage other sorts of external protocol stacks, for example to orchestrate connection setups that require coordinated actions at all endpoints in a multicast group. Our tools are fault-tolerant and secure; they can safely distribute session keys or handle delicate synchronization tasks that would otherwise complicate the managed stacks and potentially interfere with their quality-of-service objectives. Moreover, Maestro can automatically track subgroup membership on the basis of ``properties'', facilitating its use by developers who prefer not to work directly with multicast communication interfaces.