I've used some music editing software to finally combine my narration and
background music (I'm using royalty free music from www.incompetech.com) into
one mp3 file.  I add the sound file to a slide and there's no sound during
playback.  The file plays in all other playback software such as Media
Player, etc.  Before I combined the two files into one, the narration would
playback (narration was also originally an mp3 file).  Your help is greatly
appreciated.  Thank you so much.