Diddley bow

The diddley bow is a single-stringed American instrument which influenced the development of the blues sound. It consists of a single string of baling wire tensioned between two nails on a board over a glass bottle, which is used both as a bridge and as a means to magnify the instrument's sound.

It was traditionally considered a starter or children's instrument in the Deep South, especially in the African American community, and is rarely heard outside the rural South, but it may have been influenced to some degree by West African instruments. Other nicknames for this instrument include "jitterbug" or "one-string", while an ethnomusicologist would formally call it a "monochord zither".

The diddley bow derives from instruments used in West Africa. There, they were often played by children, one beating the string with sticks and the other changing the pitch by moving a slide up and down. The instrument was then developed as a children's toy by slaves in the United States. They were first documented in the rural South by researchers in the 1930s.

The diddley bow is typically homemade, consisting usually of a wooden board and a single wire string stretched between two screws, and played by plucking while varying the pitch with a metal or glass slide held in the other hand. A glass bottle is usually used as the bridge, which helps amplify the sound. The diddley bow was traditionally considered an "entry-level" instrument, normally played by adolescent boys, who then graduate to a "normal" guitar if they show promise on the diddley bow. However currently, the diddley bow is also played by professional players as a solo as well as an accompaniment instrument.

The diddley bow is significant to blues music in that many blues guitarists got their start playing it as children, as well as the fact that, like the slide guitar, it is played with a slide. However, because it was considered a children's instrument, very few musicians continued to play the diddley bow once they reached adulthood. The diddley bow is therefore not well represented in recordings.

...
Wikipedia