Originally Posted by BetterRed
Put a file link to the MP3 in the Comments - it's HTML so something like
<a href="file:///whatever.mp3/">MP3 File</a>
should do the trick. You'd then play it from Book Details - click on it and it should invoke whatever program you have associated with MP3's - WMP, WinAmp, Squawkbox etc - Note Calibre needs to have triple slash in file & folder URI's.
Thanks a lot for this trick!!