First Electric Guitar
In the 30's of the twentieth century guitars had to be louder. Before the first electric guitar was invented, people tried several things to do that.
They tried bigger bodies and John Dopyera, who was a guitar builder in Los Angeles, made his guitars louder by using metal resonators. It is the Resonator guitar.
You can still buy this guitars today! Mark Knopfler used it for its specific sound. A beautiful picture of it you can find on the album Brothers In Arms.
This guitars were louder, but still not loud enough.