it’s a complex question, because you’ll find quite different audio usage scenarios in practice.
- motion graphics, based on audio envelope curves
- video clip processing, monitoring/preserving the included audio tracks
- remote control and sync of external audio applications
the cases 1. and 2. are very common. most applications handle this kind of stuff by using audio subsystems, which work in parallel to the openfx image processing, usually also utilizing different kinds of plugin architecture (VST, LV2, etc). the openfx standard doesn’t have any support for this kind of multimedia handling until now.
remote transport control and synchronization between different applications is more unusual approach. it’s quite easy to realize this kind of linked behavior between blenders video sequence editor and ardour by jack transport control for example. whenever you chance the position in the timeline, toggle playback, etc, it will do the same in both application. this is a very powerful feature in studio environments, to combine the power of specialized tools for different tasks. in practice it doesn’t come without effort to setup and operate. it fits better to huge mastering jobs, than just audible feedback while editing or creating visual effects in sync to the audio track. from a technical point of view, it looks a little bit less demanding at first sight, because you do not have to handle the actual audio processing within the application, but in fact you need just the same amount of code at the end, to support this kind of transport control in a satisfying manner.