Ok, thats how I understand this:
Pitch angle or Blade angle = [helix angle (TAS vs Rotational Speed)]+AoA
Helix angle increases if TAS increases or RS decreases.
Helix angle decreases if TAS decreases or RS increases.
"My own would be that a CS prop changes its propeller PITCH constantly to maintain a given revoultion setting, correcting either for increased/decreased airspeed or MP". TRUE.
CSP tries to maintain the RPM, it is done by means of increase or decrease the Torque (Which is the cool name for Prop Drag, and Thrust is Lift in that analogy...), Torque increases with AoA.
....
"What about increased/decreased MP? Wouldn't an increase in MP in an essence be an attempt to increase propeller revolutions - which is then maintained constant by govenpor changing pitch/maintaining AOA?"
MP= Manifold Pressure? I suppose.
True Again.
More MP means more Power then the force leading the prop will be increased as a result an acceletarion will be there ( Unbalanced force means acc), to avoid this acc the governor increases the AoA (Setting a "Coarser" pitch)increasing the Torque (Drag) hence RPMs are maintained.
My two cents.