making of a moller 75  

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Its hard to see whats really going on there, at first it looks like a plain mortised taper* done on the lathe but that doesn't look quite right, perhaps most of it is turned and then the area where the seat joins is finished with spokeshaves and a convex file.
*mortised either before and plugged then turned or mortised after turning in a jig
Sorry does that makes sense? Probably not.
A fine oppurtunity to post a picture of just about the prettiest tool money can buy...I've got a cheap one but it chatters, probably me being useless but am hoping I'll have better luck with these.

It makes sense, Heath. I was...
It makes sense, Heath. I was thinking the same as you, but as I am using the idea of the legs on a creation of my own, I was wondering if there was an easier, more 'engineered' way to do this...
What are these tools? Spokeshaves?

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There are all sorts of shaping jigs that can be devised, I think Wegner was a bit of a master at it, usually there is some sort of guide against which a shaper cutter (like a router bit but bigger) runs. There would almost always be a bit of hand filing and sanding to tidy things up.
Did you ever see the asymetrical turning for the round chair that was shown on the dkvogue video? I think there was also something that was once used for that sort of thing called a pantograph but am not sure about that.
Do you have a pic of the chair without a seat pad or cord? I worked out a way of doing something similar a while ago with a kd fitting and sanding out the end of seat member on a drum sander, having a convex surface mating a concave surface like that might help resist any twist but it'd need testing.
There are more experienced folk than me on here though, perhaps they have some better ideas.
Yes, spokeshaves...should arrive in a couple of weeks, if only I can get some shed time...

this is roughly what I intended
as pictured

Do you have a lathe and table...
Do you have a lathe and table saw? Think about turning an accurate balnk on the lathe, leaving the top sqaure and making ajig to hold the leg in a sled and saw off the excess and hand finish the rest or use a round over bit to blend the top front edge with the rest of the leg...
Have you seen the leg treatment on the Barber Osgerby Home tables and Portsmouth Bench? Similar effect, much much simpler.