 When the F-clef is placed on the fourth line, it is called the bass ( ) clef.This is the only F-clef used today so that the terms "F-clef" and "bass clef" are often regarded as synonymous.This clef is used for the cello, euphonium, double bass, bass guitar, bassoon, contrabassoon, trombone, baritone horn, tuba, and timpani.