Liked the video's and seeing these out on the trail. Are you wanting to make these just for entertainment or for entertainment and a little bit of teaching?
For me, I don't care to hear music at all. I can turn music on my computer on if I want to listen while I watch.
I'd love to hear the engines/scraping but more than that I would like to hear why a certain line was picked or what the driver is attempting to accomplish. Even being near the spotter so you can hear what they are telling the driver is good. I also like the lower shots where you can see the lower part of the vehicle or under it and how it's flexing, moving over rocks and such.
Keep recording and showing us these great spots!