This has happened to me in two separate presentations. I've designated a file to begin on a click, but it wants to play automatically. Then when I actually click, it begins playing a second time, simultaneously with the first play.
MacBook Pro
I think I found the problem, so I'll explain here in case anyone else has a similar issue:
If you drag audio onto the canvas from your desktop or finder, it will automatically play when the presentation transitions to that slide. The audio will only play on click if you choose it from the MEDIA menu. From there you can use the builder to designate how and when you want audio files to play.
I ended up deleting the slide and starting again from scratch, only selecting audio to play from the media menu.
I think I found the problem, so I'll explain here in case anyone else has a similar issue:
If you drag audio onto the canvas from your desktop or finder, it will automatically play when the presentation transitions to that slide. The audio will only play on click if you choose it from the MEDIA menu. From there you can use the builder to designate how and when you want audio files to play.
I ended up deleting the slide and starting again from scratch, only selecting audio to play from the media menu.
This depends on which version of Keynote you are using.
In Keynote 6.1 drag and drop a file from the finder
select the file: Animate > Build In > Build Order > Start:
in the drop down menu select either On Click or Start after Transition
Audio file starts playing automatically on a slide, even though I've designated it to start "on click"
