Thank you Sylvain.
I was able to embed the mp3 file and play it with a press of a button. Unfortunately, unlike in the case of "referenced" (external) files, autoplay doesn't seem to work for embedded files (I've checked that on TiddlyWiki.com as well).
When I put this into a tiddler and then open that tiddler, the sound does not play:
<audio controls autoplay>
<source src="TiddlyWiki.mp3" type="audio/mp3">
</audio>
Is there anything else I'd need to do for autoplay to work for embedded files?
Thanks again,
Hubert