Hypothetical Emscripten <audio> based player

dom_audio_library.js

mergeInto(LibraryManager.library, {
  preloaded_audio: {},
  preload_audio__deps: ['preloaded_audio'],
  preload_audio: function(id, url) {
    let audio = new Audio(UTF8ToString(url));
    _preloaded_audio[id] = audio;
    audio.preload = 'auto';
  },
  play_audio: function(id, loop) {
    let audio = _preloaded_audio[id];
    audio.loop = !!loop;
    audio.play().catch(e => {
      let deferPlay = () => {
        audio.play().then(() => {
          document.body.removeEventListener(
            'keydown', deferPlay);
        });
      };
      document.body.addEventListener(
        'keydown', deferPlay);
    });
  },
});

play_audio.cpp

extern "C" {
  void preload_audio(int audioId, const char *url);
  void play_audio(int audioId, bool loop);
}
enum {
  AUDIO_BG_MUSIC = 0,
  AUDIO_SFX1,
  AUDIO_SFX2
};
int main() {
  char *urls[]={"music.mp3","sfx1.wav","sfx2.wav"};
  for(int i=0;i<sizeof(urls)/sizeof(urls[0]);++i)
    preload_audio(i, urls[i]);
  play_audio(AUDIO_BG_MUSIC, /*loop=*/true);
  // ...
}