Once you select one of the tracks from either our SmartSlides music library or your own uploaded songs, you will see two Beat-Matching targets once you reach the image upload step. The two targets, Slow & Uptempo, let you know how many images will be needed to enable beat-matching for the song.
The difference between the two targets is how quickly the images change during the slideshow. The Slow option will have a smaller number of transitions and images will be shown for a longer period of time. Whereas the Uptempo option will have a greater number of transitions and images will be shown for a shorter period of time.
If neither of these targets is met when you initially upload your images, you can still use the Beat-Matching Toggle at the top to learn what changes can be made to enable Beat-Matching for your song segment: