Query: What is the round-back mandolin made of? 
Context: There are many styles of mandolin, but four are common, the Neapolitan or round-backed mandolin, the carved-top mandolin and the flat-backed mandolin. The round-back has a deep bottom, constructed of strips of wood, glued together into a bowl. The carved-top or arch-top mandolin has a much shallower, arched back, and an arched top—both carved out of wood.