So, if you’re playing audio from UMG in general, you just need to emulate the way we play audio for UMG with any sound asset. Check out FSlateSoundDevice::PlaySound to see how that’s done. The media sound wave is inherits from the same class as a regular sound wave so you can use it where you would normal sound waves. So, for example, you can create a sound cue, add a wave player node, then drop your media wave in the wave reference entry for the wave player. Then once you have that you can module the audio like you can anything else – for example, you can select the “output” node and change the sound class. Or you can add a manual volume modulator, etc.
All you need to do is play the sound cue before you play the media player. The code for the media sound wave automatically knows what media player it’s associated with and “procedurally generates” the audio for the sound from the playing video. There are currently some issues with sync (especially if the video loops and you drop in and out of PIE) that we are planning on fixing in the future.
Here’s a screenshot of a sound cue that I just tested that uses the media wave instead of a normal wave:
