HTMLMediaElement.preservesPitch

<audio controls src="https://mdn.github.io/webaudio-examples/audio-basics/outfoxing.mp3"></audio>

<div>
  <label for="rate">Adjust playback rate:</label>
  <input id="rate" type="range" min="0.25" max="3" step="0.05" value="1">
</div>

<div>
  <label for="pitch">Preserve pitch:</label>
  <input type="checkbox" id="pitch" name="pitch" checked>
</div>

const audio = document.querySelector("audio");

const rate = document.querySelector('#rate');
rate.addEventListener('input', () => audio.playbackRate = rate.value );

const pitch = document.querySelector('#pitch');
pitch.addEventListener('change', () => {
  audio.mozPreservesPitch = pitch.checked;
  audio.preservesPitch = pitch.checked;
});