Same on the Pitts, I have many hours on S2B and I can say : when you cut the throttle the sound change a lot ! yes the prop "rpm" rest stable above a certain speed , and the sound of the prop rest constant and it is dominant, but not the engine sound !
It is like in a car if you stay in 4th gear with throttle at 5000 rpm on a flat road and if after in a descent with no throttle you maintain the same 5000 rpm still in 4th gear but with only the brakes ! You have the same engine rotation but not the same sound because of no or little combustion in the engine !
So we have 2 sounds for the engine : the rotation sound (in some way merge with the prop) and the combustion sound .
Exactly.. Zero throttle surely means zero (or idle) combustion. It seems like little or no percentage of the the engine sound is caused by combustion or more significantly exhaust?
The IL-2 series are about to introduce a P38 so it will be interesting to see their take on it with their record of attention to detail and accuracy.