Developing computer systems that are both concurrent and evolving is challenging. To guarantee consistent access to resources by concurrent software components, some synchronization is required. A synchronization logic, or policy, is at present entangled in the component code. Adding a new component or modifying existing components, which may require a change of the (global) synchronization policy, is therefore subjected to an extensive inspection of the complete code. We propose a calculus of concurrency combinators that allows a program code and its synchronization policy to be expressed separately; the policies include true parallelism, sequentiality, and isolation-only transactions. The calculus is equipped with an operational semantics and a type system. The type system is used to verify if a synchronization policy declared using combinators can be satisfied by program execution.