Jack, I was surprised to see... "A "fluted" metal washboard was patented in the United States by Stephen Rust in 1833. Zinc washboards were manufactured in the United States from the middle of the 19th century." (Wiki) I was further floored to learn that "trumpet-like instruments have historically been used as signaling devices in battle or hunting, with examples dating back to at least 1500 BC. They began to be used as musical instruments only in the late 14th or early 15th century." (Wiki) My junk art mechanically amplified Nobro guitar designs include my own hybridization of previous design aspects employed by the two primary forms that have been around for the last 100 years, as well as my own unique ideas about the concept. I've been taking some time to work on my fourth build, my Newbro, for the last few days. It pushes farther away from any previous notions created, into the unknown land of invention but even this latest build has its basis rooted in the notions about resophonic guitar designs first created around 100 years ago. My guitars are just my unique spin of the concept of mechanical amplification.