I was just about to write: simply plug them together.
But I think I know where you are struggling: A MixerAudioSource is not a PositionableAudioSource. I stumbled there a couple years back as well.
Unfortunately it means, you have to write your own PositionableMixerAudioSource yourself.
You can copy the whole MixerAudioSource, but instead:
- inherit from PositionableAudioSource instead of AudioSource
- change the input sources to accept only PositionableAudioSources instead of AudioSource
- Implement the additional four abstract methods of PositionalAudioSource
– getNextReadPosition : probably use the information from the first for a start
– getTotalLength : probably use the information from the first for a start
– isLooping : probably use the information from the first for a start
– setNextReadPosition : call this for all sources
Hope that helps