abstract class Sound {

 Sound() {
   var initEngine = SoundMixer.engine;
 }

 static Future<Sound> load(String url, [SoundLoadOptions soundLoadOptions = null]) {

   switch(SoundMixer.engine) {
     case "WebAudioApi" : return WebAudioApiSound.load(url, soundLoadOptions);
     case "AudioElement": return AudioElementSound.load(url, soundLoadOptions);
     default            : return MockSound.load(url, soundLoadOptions);
   }
 }

 static SoundLoadOptions defaultLoadOptions = new SoundLoadOptions(mp3:true, mp4:true, ogg:true, wav:true);

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

 num get length;
 SoundChannel play([bool loop = false, SoundTransform soundTransform]);

}