I have tried to find which of the plethora of tags controls the width of the mediaelement.js audio player but can't seem to work it out.
I'm assuming it's a combination of the tags that need to be edited?
I downloaded the player from the mediaelemenjs.com and the CSS for it is huge.
<div class="fluid player">
<audio id="player2" src="http://www.newlifedeewhy.com/media/school/2014/20140526-School-EpiLimiƱana.mp3" type="audio/mp3" controls></audio>
<script>$('audio,video').mediaelementplayer();</script>
</div>
Here is JS Fiddle for demonstration.
you can find the option at the API list
eg: