Dopyera

After further refinements, Dopyera applied for a patent on the so-called tri-cone guitar on April 9, 1927.

He first conceived of a guitar fitted with a phonograph-like amplifying horn, and approached inventor and violin-maker John Dopyera to create a prototype which proved to be, by all accounts, a failure.

Thereafter, Dopyera and his brothers began to make the tri-cone guitars in their Los Angeles shop, calling the new guitars "Nationals".

These efforts produced an instrument which so pleased Beauchamp that he told Dopyera that they should go into business to manufacture them.

They are sometimes known as Dobros after the Dopyera brothers, whose company first made them.