What was found
(CAN) AFTER STARTING A NORMAL DESCENT, PILOT REPORTED THAT THE PROP RPM FOLLOWED THE N1 AS THE POWER WAS REDUCED. THE PILOT INCREASED THE N1 AGAIN TO FIND THE PROP RPM ALSO INCREASED. THEN, THEY HEARD AN UNUSUAL ENGINE SOUND AND THE PROP FEATHERED ITSELF. THE CREW REDUCED THE POWER AND KEPT THE ENGINE RUNNING AT IDLE UNTIL A SAFE EMERGENCY LANDING WAS MADE. TROUBLESHOOTING ONGOING.