The bass guitar is a stringed instrument (usually four-string) used in many forms of modern non-classical music. The tuning is standard ’E – ‘A – D – G; like a double bass and similar to the lowest four strings of a guitar, but an octave lower. Usually a bass guitar is made with frets, although fretless bass guitars also exist.

Most bass guitars are electric or semi-acoustic, but acoustic bass guitars have also been made. The acoustic bass guitar cannot really be used without amplification and is usually used in acoustic ensembles such as mariachi orchestras (where a gitarron (mexicano), a very large six-string acoustic bass guitar with a very large sound box, is usually used). The sound is more like that of a double bass played pizzicato.