Interesting Reg, and what's even more amazing, is at least the first few recordings were only 4 tracks.  I suppose they did some of the tracks with the whole band recorded at once, then only overdubbed a little, unlike the recordings now, with 24 and up tracks, digitalized and etc...

I'm probably a good bit older than you, and I saw them live TWICE, I think 70, then again in 71, at the Montreal Forum.  Both shows were great...complete with violin bow, Plant histrionics, and Bonham smashing that huge Chinese gong (or whatever that thing was ).  Not to mention all the hash at those concerts...and the traditional "light the lighter" at the end, so we could see how many thousands of us were there.   Yeah, I suppose you "had to be there".  One of the shows, I think the first one, they opened up the lights in the arena, and they played "Rock n' Roll" full tilt, as an encore...kicked major ass (a good few years before the thing was actually released on an album).

Keep on Rockin',

Gene