A resonator guitar is an acoustic guitar that produces sound by transmitting string vibrations across the bridge to one or more spinning metal cones, or resonators. This creates a unique ear-tingling sound. From design, they play quieter than standard acoustic guitars. Because of this, horns and rhythm instruments in dance orchestras easily overshadowed resonator guitars. However, they still had an admired distinctive sound. Styles such as bluegrass and blues adopted the instrument after amplification addressed the volume problem. Their tone has been compared to liquid, which has been translated to complicated overtones, a reverberating consistency, and a lot of sustain. 

During the beginning of the 20th century, many musicians were in need of instruments that could be heard in loud environments. Environments such as a bandstand, juke joint, or a crowded downtown sidewalk. Several American manufacturers developed the guitar to suit those demands. They started constructing larger and larger instruments and experimenting with various design techniques. For instance, they tested innovative bracing mechanisms and mechanical amplification. 

Eventually, John Dopyera designed a way to make the guitar louder using three very thin aluminum cones, driven by the strings and vibrating a T-shaped formed bridge. Later on, the National String Instrument Corporation, also called just National, implemented a less complex concept. It was more cost-effective to build, understood as a reaction to the Great Depression. This less expensive design used a large tube, called a biscuit, with a narrow bridge added to the top of the pole. 

Construction of the resonator guitar

A resonator guitar’s body can be made of wood, metal, or on occasion, other materials. There are usually two main sound openings, located on either side of the fingerboard extension. The sound holes in single-cone versions are symmetrical and either oval or f-shaped. On the other hand, the older tri-cone design has irregularly shaped sound holes.

Resonator guitars are of two different styles: 

  • Square-necked guitars, as played in lap steel guitar style
  • Round-necked instruments played as a traditional guitar or steel guitar.

There are three primary resonator prototypes for these guitars:

  • The tri-cone, designed by the first National firm, with three metal cones
  • The single-cone “biscuit” design of other National instruments
  • The single inverted-cone design, also known as a spider bridge, of Dobro brand instruments and instruments that copy the Dobro design

Manufacturers have made variations of all these designs under different brand names. Additionally, some contemporary instruments also incorporate electrical pickups and similar technologies.