I have recorded a stand-alone audio file and now I want to match it up with a slide deck video file from Powerpoint, but I need each slide to be a different duration. To do this on a Mac, I learned that I have to do the following: 1. Go to Slide Show and UNCHECK the "Use Timings" feature. 2. Go to Transitions and Check and Edit the time in the "After" section to match the number of seconds desired for that slide (do this for each slide). 3. Go to File > Export > File Format > MP4 (or MOV) and make sure the "Use Recorded Timings and Narrations" IS checked and then change the "Seconds spent on each slide..." to 1 second. If you then review the video file, each slide should play for the exact number of seconds that were designated in the "After" field above.