class AudioElementMixer {

 List<AudioElementSoundChannel> _soundChannels = new List<AudioElementSoundChannel>();
 num _mixerVolume = 1.0;

 applySoundTransform(SoundTransform value) {
   _mixerVolume = value.volume;
   _soundChannels.forEach(_updateSoundChannel);
 }

 //-----------------------------------------------------------------------------------------------

 _addSoundChannel(AudioElementSoundChannel audioElementSoundChannel) {
   _soundChannels.add(audioElementSoundChannel);
 }

 _removeSoundChannel(AudioElementSoundChannel audioElementSoundChannel) {
   _soundChannels.remove(audioElementSoundChannel);
 }

 _updateSoundChannel(AudioElementSoundChannel audioElementSoundChannel) {

   var audio = audioElementSoundChannel._audio;
   var channelVolume = audioElementSoundChannel._soundTransform.volume;

   if (audio != null) {
     audio.volume = _mixerVolume * channelVolume;
   }
 }
}