js/midi-player.html

<div>
    <midi-visualizer type="piano-roll" id="myPianoRollVisualizer"
        src="input.midi">
    </midi-visualizer>
    <midi-player
        src="input.midi"
        sound-font visualizer="#myPianoRollVisualizer">
    </midi-player>

    <h1>test</h1>
</div>