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. 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".