You can turn your slideshow into a video podcast with sophisticated audio effects by exporting to GarageBand.
In Keynote, choose Share > Send To > GarageBand.
Choose an option from the Timing pop-up menu:
Recorded Timing: If you recorded your slideshow (as described in Recording a Voiceover Narration), your slideshow movie plays using the timing you recorded.
Fixed Timing: Viewers can’t control when the movie advances; the movie plays using the timing you specify in the next step.
If you choose Fixed Timing, type values in the duration fields:
Slide Duration: How long each fully built slide remains on the screen after the last object build is complete.
Build Duration: The number of seconds between the beginning of one build stage and the next in each object build. There is no delay between the moment a slide first appears on the screen and the first stage of an object build.
To include the slideshow soundtrack or the recorded audio, select the Audio checkbox.
Click Send.
Type a title and choose a location for your slideshow, and click Export.
If GarageBand wasn’t open, it opens. Your slideshow is imported as a movie.