The authors explore perceived sound properties of acoustic guitars built with foamed polycarbonate soundboards rather than spruce or cedar. The research seeks to establish the extent to which polymer acoustic guitars are an acoustically credible alternative to wood instruments. Data are generated through participation by members of the public (n = 320) in blind listening tests. Remarkably, participants are found unable to distinguish much beyond a 50% success rate whether sound originates from wood or polymer acoustic guitars. The findings challenge deeply rooted ideas about traditional material-instrument relationships and champion the use of design as a driver for instrument innovation and artistic engagement.