Can I add the "your browser does not support audio" message when I use the <source> method

Answer 1

This will do the work ..
<audio controls>
<source src="" type="audio/mpeg">
Your browser doesn't support audio
</audio>
Sir, Please do upvote :)

Answer 2

Yes
<audio controls>
<source src="" type="audio/mpeg">
Please update your browser.
</audio>