Mechanical engineer Robert Langdon plays traditional music on mandolin, guitar, dobro, banjo, and violin. He has always built things in his spare time, including musical instruments. So after retiring, he decided to make a violin. Keenly interested in the physics of sound, he experimented with sheet aluminum he had laying around. This is one of eight aluminum violins he has made to date. He machines the patterns, then cuts the aluminum with a jigsaw, sometimes roughing out a shape with scissors first. Robert's violins sound remarkably like ones made of wood. As he describes, "It performs quite well over a microphone . . . I try to avoid using it in electrical storms."