What was found
(CAN) DEPARTED AIRPORT AND LEVELED OFF AT FL410. VERY LIGHT TURBULENCE WAS ENCOUNTERED. APPROXIMATELY TWO MINUTES INTO CRUISE, THE RT ENGINE PRODUCED A LIGHT BANG & BEGAN TO SPOOL DOWN. THE RPM'S SETTLED A T 25-30 PERCENT. THE R/H THROTTLE WAS REDUCED TO IDLE THEN TO IDLE CUT-OFF. DURING THE DESCENT, AT FL380 THE LT ENGINE BEGUN TO VIBRATE, FOLLOWED BY AN ILLUMINATION OF THE LT GENERATOR WARNING LIGHT. AT THIS TIME AN EMERGENCY WAS DECLARED & A DESCENDING TURN WAS INITIATED.