There are several plugins which claim to do that, here's one for example: https://wordpress.org/plugins/wp-music/


You can also use the standard audio player which comes with WP. Just set the loop and autoplay attributes to on:


[audio src="..." loop="on" autoplay="on"]


You can even hide it in the background:


<div style="display: none">[audio src="..." loop="on" autoplay="on"]</div>