In the early ‘20s a Vaudeville guitar player named George Beauchamp paid a visit to a stringed instrument shop. His complaint: no matter how loud he played, his guitar just couldn’t compete with the rest of the instruments in the orchestra.
So, the owner of that shop, John Dopyera, developed the idea of fitting a guitar body with aluminum cones. Discs of fine-spun aluminum that vibrate to amplify sound. Make the body out of metal, and you’ve got a National guitar.