when playing a preview, the music is always much louder than the existing video audio, even if you have loud selected as the audio option for each slide. when you finalize and download, the music levels drop precipitously and the audio from your imported video returns to a more normal level. this usually results in having to tinker many times with exporting the video from spark, testing the audio level of the music blind multiple times until you get it right. there is no reason whatsoever the system shouldn't just be able to play the correct audio when i hit preview.