I was a little surprised to see that there is no bonus content for this besides the manual. Myst has an incredible soundtrack which I still listen to today. I thought the CD's were out of print, but maybe they're still in distribution, hence no soundtrack.. but there was an incredible Making Of Myst video that I have ONLY seen once, way back on the Sega Saturn version of Myst. I was deeply saddened when it wasn't on the PSX version once I finally got my own copy of it.
I dunno, I guess I was hoping for a little something more. "Making Of...", some wallpapers, anything else... you know?

Now that you mention it, I do remember seeing something about the sound production. The comments on YouTube indicate it was on the original Myst CD.
So instead of wasting more time on Google, I looked. And it is. It's a ~70MB .mov file in the qtw/making folder.

I have it on my 10th Anniversary DVD-ROM.

Not quite the same, but here are some of GameTap's little documentaries on the Myst series, from back when "GameTap TV" was a thing. They have some of the same content as the ones that came with the games.
Myst (series)
Riven
And some for the games not yet on GOG:
Myst III: Exile
Myst Online