A central issue of all approaches to composing adaptive software is a level of indirection for intercepting and redirecting interactions among program entities. It has been pointed out that separation of concerns is one of the key techniques for reconfigurable software design. In this paper we describe a general framework for the separation of concerns in concurrent applications. Concurrency issues are separated and treated as orthogonal to the system base functionality. The framework combines declarative and imperative programming and provides a powerful mechanism for synchronizing concurrent computations. We describe a particular implementation of the framework (for both uniprocessors and distributed systems) as an extension to the Java programming language, and comment on how model-based verification methods can be automatically applied to programs in the resulting language.