Annenberg Professor of Music Emeritus George Crumb rehearsing for the moment when he shook the stage with his maracas, cymbals, gourd, washtub and other percussive surprises at the premiere of his newest work, ÒMundus Canis.Ó The concert was a celebration of his 70th birthday at the Curtis Institute of Music Oct. 12. ÒMundus CanisÓ featured distinguished guitarist David Starobin and Crumb himself on percussion.