Originally Posted by
Concours77
The Electra has thrust levers, not throttles. Engines maintain approx. 13000 rpm.
Actually, on the L-188 they are power levers with output measured by torquemeters. And the constant speed props had synchronizing and syncrophasing. They were all the same speed and rotated with each blade crossing the wing at about the same time to reduce harmonic effects in normal operation.
So, as you observe, a change in acoustic pitch of the prop noise would be unusual in normal operation.