This was actually solved with some very simple html.
I Uploaded the .mp3 files to $SPLUNK_HOME/etc/apps/[MYAPP]/appserver/static and name them 1.mp3, 2.mp3...
In the single viz, I set it to populate the result into a token using the below code.
<search base="base">
<query>| head 1 | table position</query>
<progress>
<set token="position_tok">$result.position$</set>
</progress>
</search>
In a html panel I then placed the following
<html>
<body>
<audio src="/static/app/[MYAPP]/$position_tok$.mp3" autoplay="autoplay"/>
</body>
</html>
and hid the panel. Now, when the result changes, it plays the relevant mp3 file on change
