Hello Steven The Duchess use default X-Plane piston sounds for sure, look at my threads : I also agree, I'm a beta tester of incoming DreamFoil R-22, that use his own plugin, the dream engine, used by the R22, as well as the 206. It's very immersive, the sound are managed by a physical engine, it react almost like the real life, blade slap happen when it should, sound are 3d spacialized ( exemple, tail rotor sound better heard around the tail rotor etc.. ) In my opinion, a legendary aircraft such the DC-3 really should benefits serious sounds ! Varios sounds for starter, ignition, first explosion, different RPM, shutdown etc.. but not only high quality like in FSX, high quality sounds that sounds like what we see..