A tremolo arm, tremolo bar or whammy bar is a lever attached to the bridge of an electric guitar that can slacken or elongate the strings temporarily, changing the pitch or creating a vibrato or pitch bend effect.
Academically speaking, the tremolo arm is most often used for vibrato, not tremolo; many sources call "tremolo" a misnomer, as Leo Fender christened it more for marketing reasons than anything else. See vibrato unit.
The first commercially successful tremolo arm was the Bigsby, invented by Paul Bigsby. The design involves a spring-loaded arm that causes a tailpiece to move, creating a vibrato. To this day, the Bigsby enjoys some popularity, especially on hollow body guitars.
The next major development was Leo Fender's "synchronized tremolo", a device which popularized the use of the term "tremolo". First released in 1954 on Fender's first legendary Stratocaster, the simple but effective design offers a greater range of pitch change in addition to a better capability for "upbends". Artists such as Jimi Hendrix and many surf music bands have used the synchronized tremolo to great effect, and has become part of the style. Many rock bands of all types have used the tremolo for all sorts of effects, especially as a vibrato over chords. One guitarist especially known for his use of the bar is Dave Gilmour of the rock band Pink Floyd. This can be heard on countless songs. The last chord of the Rush song '2112' (Grand Finale) is a common reference.
Around 1979, the locking tremolo was invented by Floyd Rose. The "locking trem" became highly popular among 1980's heavy metal guitarists due to its extremely wide range of variation and tuning stability.
