Audio in layers

I would suggest that you also confirm that the audio files are clean and play correctly outside of SL. Then verify that there is nothing on your base layer that is preventing the higher layers from playing the audio. I would also be checking the behavior by either publishing to HTML or previewing the scene, because I have observed that sometimes it’s difficult to get a clear indication of how the slide plays by using the “play” button in the timeline or simply previewing the slide.