A resonator guitar is an acoustic guitar whose sound is produced by one or more spun metal cones (resonators) instead of the wooden soundboard (top). Resonator guitars were originally designed to be louder than regular acoustic guitars, which were overwhelmed by the horns and percussion instruments in orchestras. They became prized for their distinctive sound, however, and found life with several musical styles—most notably bluegrass and the blues—well after electric amplification solved the issue of inadequate guitar sound levels.
Resonator guitars are usually of two styles: square-necked guitars played in steel guitar style and round-necked guitars played conventional style or lap-steel-guitar style. Resonator guitars are popularly used in blues and bluegrass music. Traditionally, blues players favor round-necked guitars, often played with a bottleneck slide, while bluegrass players used square-necked Dobro-style instruments played as a steel guitar. Resonator guitars, however, can be used in a wide variety of musical contexts.
The resonator guitar is perhaps most often played as a lap steel guitar, and the more common square-necked version is limited to this playing position. Square-necked instruments are always set up with the high action, favored by steel guitar players, and tuned to a suitable open tuning.
The round-necked version is equally capable in either lap steel or traditional Spanish guitar position. It may be set up with a variety of action heights, ranging from the half inch favored for steel guitar (making use of the frets almost impossible) to the small fraction of an inch used by conventional guitarists. A compromise is most common, allowing use of a bottleneck on the top strings but also use of the frets as desired, with the guitar played in the conventional position.
Many different tunings are used with resonator guitars. Some square-neck tunings are not recommended for round-neck resonator guitars, owing to the high string tension required, which in turn requires the stronger square neck. Slack-key guitar tunings are most suitable for bottleneck playing and conventional E-A-D-G-B-E guitar tuning is also popular.