<audio id="aud" src="https://music.163.com/song/media/outer/url?id=31654479" autoplay loop controls></audio>

<script>
const setVolume = (val) => Math.min(1, Math.max(0, val));

document.addEventListener('keydown', e => {
	if(!e.altKey) return;
	switch (e.keyCode) {
		case 88: //X
			aud.paused ? aud.play() : aud.pause();
			break;
		case 74: //J
			aud.muted = !aud.muted;
			break;
		case 187: case 107: //+
			aud.volume = setVolume(aud.volume + 0.1);
			break;
		case 189: case 109: //-
			aud.volume = setVolume(aud.volume - 0.1);
			break;
		default:
			return;
	}
});
</script>