Callas's voice was noted for its three distinct registers: Her low or chest register was extremely dark and almost baritonal in power, and she used this part of her voice for dramatic effect, often going into this register much higher on the scale than most sopranos. Her middle register had a peculiar and highly personal sound—"part oboe, part clarinet", as Claudia Cassidy described it—and was noted for its veiled or "bottled" sound, as if she were singing into a jug. Walter Legge, husband of diva Elisabeth Schwarzkopf, attributed this sound to the "extraordinary formation of her upper palate, shaped like a Gothic arch, not the Romanesque arch of the normal mouth".