Contextual Associations

The dobro is a plucked box-lute chordophone initially developed and manufactured in the United States. It has subsequently come to be distributed and manufactured internationally. Basically a significantly modified form of the classical guitar, which is of European origin, the dobro is designed to produce a much higher volume of sound with the addition of an aluminum bowl-shaped resonator built into the conventional guitar resonator, and by being strung with steel strings. Furthermore, the dobro departs from the classical guitar in another important way--it is played with its back lying across the player’s lap, in the style of the acoustic Hawaiian steel guitar. The strongest stylistic association for the dobro is with country music.

Description

The resonator section of the instrument’s string carrier is really a bowl resonator within a box resonator. The sides/ribs and back of the general resonator are made of mahogany much in the style of a conventional flattop guitar. Its soundboard, however, differs considerably in that, instead of having a 3-4 inches in diameter soundhole, it has a much larger hole (approximately 10 inches in diameter) into which is inserted a specially designed bowl-shaped aluminum resonator; additionally, there are two small soundholes in the wood soundboard covered with mesh flanking the end of the fingerboard. What is visible from the exterior is the perforated metal ‘lid’ of the bowl resonator, on which rests a special wooden bridge with a small gap in its middle. A screw in this gap connects the bridge to the intersection of two ‘spider’ rods the ends of which are connected to the lip of the bowl resonator. These rods help support the lid of the resonator and also help transmit the energy of vibrating strings to the bowl resonator below (in the first detail image, taken from the bottom end of the instrument, the back of the gapped bridge and the connecting screw in its middle can be seen). The metal resonating chamber has a central dome that rises up to the intersection of the spider rods at the base of the bridge. The neck of the dobro is unusually thick and square in its profile (see second detail image). Made of mahogany with a flat fingerboard of ebony glued to its topside, the fingerboard has nineteen metal frets inserted in grooves cut across it. The bottom end of the fingerboard continues onto the soundboard, the neck securely joined to the resonator at the twelfth fret. The top end of the fingerboard terminates in a high nut, which is a raised bridge that separates the fingerboard from the integral tuning block. This dobro is outfitted with six strings, the top two are wire and the bottom four have steel cores wound with brass. The bottom ends of the strings are attached to a metal tailpiece and run in a parallel plane over the bridge and above the fretted fingerboard before passing over the nut (see the first detail photo). The other ends of the strings are wound around the capstans of the back-mounted metal machine heads with their laterally situated knobs. The acoustically active length of the strings is 25 inches.

Player - Instrument Interface and Sound Production

The seated performer rests the dobro across his or her lap with the neck to their left and the strings facing upwards. The thumb and fingers of the right hand are used to pluck the strings, which are free stopped with a 'bottleneck.' The bottleneck for this instrument is made of steel and looks like a tiny I-beam with one rounded side. Held in the player’s left hand, the bottleneck is pressed firmly against the strings but not with enough pressure to press them against the frets, which are present primarily as a visual guide for the performer. This method of stopping the strings allows the performer to produce sliding pitch inflections and to have precise control over the amplitude of vibrato. Harmonics can also be produced by lightly touching the strings with the bottleneck. This dobro is currently tuned to ‘open A’ tuning: A2 - C-sharp3 - E3 - A3 - C-sharp4 - E4, one of several tunings associated not only with the dobro but also the Hawaiian steel/lap guitar. The basic range of the dobro in this tuning is A2 - B5, about three and a half octaves.

Origins/History/Evolution

The dobro evolved most directly from of the Hawaiian steel guitar or lap steel. The Czech-born American John Dopyera is credited with its creation in 1925. It can generically be labeled a ‘resophonic’ instrument, a term for any guitar-like instrument with one or more metal resonating bowls inserted into a surrounding resonator. Many such instruments were being designed in built during the 1920s and 1930s to provide guitarists with louder instruments in pre-amplification times. Despite being made largely obsolete by electric Hawaiian steel guitars, the dobro has survived to the present day primarily amongst country music and bluegrass artists.

Bibliographic Citations

Davies, Hugh. 1984. "Dobro" NGDMI v.1: 577-578.

Ross, Gordon. 2003. “The Guitar in Country Music,” in The Cambridge Companion to the Guitar, Victor Anand Choelho, ed. Cambridge: Cambridge University Press, pp. 133-149.

Turnbull, Harvey, and Tony Bacon. 1984. "Guitar, 7" NGDMI v.2: 103-105.