Acoustic Hollow Body Resonator guitar
Nickel-silver body and mahogany neck
At the request of guitarist George Beauchamp, John Dopyera produced the first resonant guitar around 1925. The principle was simple: a thin aluminum funnel shape was placed inside the body like a loudspeaker and made direct contact with the bridge saddle. When the guitar strings were struck, the cone amplified the vibrations.
This experiment was very successful and in 1927 Dopyera and Beauchamp founded the National String Instrument Corporation. The first instrument that this company produced was a metal-body guitar with three aluminum funnel-shaped resonators inserted, connected by a T-shaped aluminum bridge to which a mahogany bridge saddle was attached. This system was called the Tricone.
The National String Instrument Corporation produced four Tricone Models, after which Dopyera founded his own company, Dobro. The models differ only in the engraved decorations on the guitar top.