Loading additional source audio during progressive load

We have a custom integration (python api) running in RV, which is responsible for swapping in high quality proxy media during progressive load. Currently using the setReturnContent() method in a function bound to the incoming-source-path event. This enables us to provide a single, custom source media path.

Is it possible to provide multiple media paths using this method? Ideally, want to load video AND separate audio media to the source. Are there other suggested methods to achieve this? Load speed and efficiency is our main priority.

Thanks all!