1. Click on Insert -> Audio -> Audio Browser (or Audio from File).
  2. Select which audio track you want to play.
  3. Powerpoint.2011.Insert.Audio
  4. Click and drag Audio Track over.
  5. Click on Audio Icon.
  6. Click on ‘Format Audio’ tab.
  7. Under ‘Start’ select: ‘Play Across Slides.’
  8. PowerPoint.2011.Format.Audio.Toolbar
    It’s that simple. If you want to do this for only a certain number of slides, follow the steps above and then follow the ones below.
  9. Click on the ‘Animations’ tab.
  10. Click on the ‘Reorder’ button.
  11. Powerpoint.2011.Animation.Reorder
  12. Click on the animation you want to change.
  13. Under Media options, change it from ’999′ to however many slides you wish to play the media across.
  14. PowerPoint.2011.Custom.Animation