Aspect-Oriented Programming (AOP) is concerned with the modularization of crosscutting functionalities. Such functionalities are problematic, in particular, for the development of concurrent applications, such as graphical user interfaces or multithreaded server applications. However, few approaches address this problem: there is, in particular, no general model for concurrent AOP that enables coordination among concurrently-executing aspects as well as coordination of concurrent aspects and base applications. In this paper, we discuss general requirements for such models, briefly present a specific instance meeting these requirements, and propose a set of general composition operators for the construction of concurrent applications using concurrently executing advice.