1. A method comprising: generating a multi-level, branched hierarchical structure of components that input, process, and output audio data; wherein each of the components implements a messaging interface that conforms to a common interface abstraction; at a first component of the hierarchical structure that is processing an audio stream, receiving, separately from the audio stream, a control message via the messaging interface of the first component, the control message specifying a change to the manner in which the audio stream is being processed by the hierarchical structure, wherein the control message is different from the audio stream; the first component forwarding the control message to one or more other components of the hierarchical structure via the messaging interfaces of the one or more other components; at least a second component of the hierarchical structure, altering a parameter affecting how the second component outputs audio data in response to the second component receiving, separately from the audio stream, the control message via the messaging interface of the second component; wherein the steps of the method are performed by one or more computing devices.