Service composition is a well-established field of research in the service community. Services are commonly regarded as black boxes with well-defined interfaces that can be recursively aggregated into new services. The black-box nature of services does not only include the service implementation but also implies the use of middleware and hardware to run the services. Thus, service composition techniques are typically limited to choosing between a set of available services. In this paper we keep the black-box nature and the principle of information hiding of services, but in addition we break up services vertically. By introducing vertical service composition, we allow services to be provisioned on-demand using the middleware and runtime environment that specifically meets user-required quality of services (QoS). Therefore, a service is setup individually for services requestors instead of providing them with a pre-determined list of available services to choose from. We introduce the concept of vertical service composition and present an extension to an enterprise service bus (ESB) that implements the concept of vertical service composition by combining concepts from provisioning with those of (dynamic) service binding.