Thanks for explaining the turbulence node in Bump thing, Bill.

As to the AO, I'm struggling a bit. Probably doing something stupid, so I'm looking at each and every symbol to make sure I didn't put a + when I was meant to put a . I tried this (leaving out stuff that hasn't changed):
**  # Specular node
  setSpec = Blinn(1,.4,.65,.4)
  
  # Sets the diffuse value, which is going to be whatever's left over from subtracting 1 from the specular value
  setDiff = 1 - setSpec
  
  # Ambient Occlusion node
  setAmbOccl = AmbientOcclusion(.7,40,.1,1)
  
  # Could also be expressed as setDiffVal = setAmbOccl   ??  trying to get my head around shortcut statements
  setDiff = setDiff * setAmbOccl
**
  # Underlying skin tone
  baseTone = Blender(colourMap, Blender(ltBlue * colourMap, ltRed * colourMap, .5).labelled("BaseTone"), .7)**

and then:
**  # Gamma-correction process
  linearColormap = setSkin ** gamma**
** 
  # And finally, that diffuse node with all values where we want them!
  setDiff = Diffuse(linearColormap,  setDiff * .7)**

and finally:
**  s.Alternate_Diffuse = (setDiff + setSpec) ** (1/gamma)**

which is no different. Preview looks fine... colours are all there. Skin renders monochrome. Obviously preview isn't going to give you all the information... long ago stopped trusting it.
What am I missing about:
spec = Blinn(...)
dv = 1 - spec
ao = AmbientOcclusion(...)
dv = dv * ao
diff = Diffuse(color, dv)

Where you said color, I'm assuming you mean my linearColormap (which includes that gamma-correction stuff), not just colourMap (the imageMap) itself? Or, if so, where to I do gamma-correction now? colourMap, btw, is referenced by a new Blend thingie where I try to bring a bit more warmth into the skin with:
**  # Underlying skin tone
  baseTone = Blender(colourMap, Blender(ltBlue * colourMap, ltRed * colourMap, .5).labelled("BaseTone"), .7)**

I feel I'm so close... attached you should find the entire script - just removed the mm1 bit...

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks