For my group’s video essay, we’ll be using lots of clips- but we’ll mostly just need them for the visual aspects, not audio. So I found out how to delete the video’s audio when working in Windows Movie Maker.
This blog post does a great job in explaining how to remove sound from videos- and even how to cut audio selectively (which is a bit harder, but certainly understandable if you take it step-by-step!) From there, any music or narration overlay can be added and not affected by the video source’s audio.
Hope this helps!