Rocket.Chat/packages/rocketchat-oembed/client/oembedAudioWidget.html

<template name="oembedAudioWidget">
	<a href="{{url}}" target="_blank">
		{{#if parsedUrl}}
			{{#if collapsed}}
				<span class="collapse-switch icon-right-dir" data-index="{{index}}" data-collapsed="{{collapsed}}"></span>
			{{else}}
				<span class="collapse-switch icon-down-dir" data-index="{{index}}" data-collapsed="{{collapsed}}"></span>
				<blockquote>
					<audio controls>
						<source src="{{url}}" type="{{headers.contentType}}">
						Your browser does not support the audio element.
					</audio>
				</blockquote>
			{{/if}}
		{{/if}}
	</a>
</template>