SoundClass->Properties.Volume doesn't work on Android devices

I am having trouble controlling the volume of a MediaPlayer on Android. This approach works perfectly on the desktop.

SoundClass = Cast<USoundClass>(StaticLoadObject(USoundClass::StaticClass(),
  NULL,
  TEXT("SoundClass'/Game/Movies/360SoundClass.360SoundClass'")));

if (SoundClass)
{
  SoundClass->Properties.Volume = NewVolume;
}

I have also tried to iterate over AAmbientSound actors, getting the AmbientSound of the scene, setting it’s AudioComponents VolumeMultiplier, or getting the main audio device with GEngine->GetMainAudioDevice() and setting the TransientMasterVolume.

All of this works flawlessly on the desktop but it stops working on Android!
I am trying this out in GearVR mode.

This is not supported on Android.

On Android, the audio data is played directly via the operating system’s sound mixer. The Engine never sees it. This is because the standard Android Media Player API does not make audio data available. There is a lower-level API that could give us access to the audio data, but it is much more involved, and we haven’t had time to implement it yet. It is currently scheduled for 4.20.

I have actually suspected that something like this would be the cause. Thank you for clarifying!