What Is Tremolo? Rapid Repetition and the Word It Gets Confused With

Tremolo varies amplitude, meaning loudness, either by repeating a note rapidly or by modulating the volume of a sustained sound. Vibrato varies frequency, meaning pitch, by oscillating around a central note. They are produced by different actions, they sound different, and they carry different associations, with vibrato adding warmth and richness to a held note and tremolo adding urgency, shimmer or agitation. The confusion is entrenched in equipment naming, since the arm on an electric guitar that changes string tension produces vibrato and is universally called a tremolo arm, while the effect circuit that modulates volume is correctly called tremolo and is sometimes labelled vibrato. That inversion is generally attributed to an early manufacturer's mislabelling and has proved impossible to correct, so the terms have to be read in context.

The technique differs completely by instrument and some versions barely resemble others:

• •Bowed strings, where a very fast short bow stroke repeats a note, producing the shimmering effect used constantly for tension in orchestral writing
• •Plucked strings, where the note is repeated with alternating fingers or rapid picking, which is fundamental to mandolin and to classical guitar
• •Voice, where rapid pulsing of the airflow produces a pronounced wobble, used in some traditions and avoided in others
• •Keyboard, where rapid alternation between two notes approximates a sustained tremolo on an instrument that cannot sustain
• •Electronic, where a circuit modulates the amplitude of the signal at an adjustable rate and depth
• •Percussion, where a roll on a drum or a mallet instrument is exactly this and is notated the same way

On several instruments the technique exists to solve a physical limitation rather than as an ornament. A plucked or struck string begins decaying immediately and cannot be held, so repeating the note rapidly is the only way to produce a sustained line, which is why mandolin playing uses it continuously and why a piano writing a long melodic note may resort to alternating octaves. The same reasoning applies to mallet percussion, where a roll is how a note is held. On instruments that can sustain, including bowed strings and winds, the technique is genuinely expressive rather than compensatory, and composers use it for effect. That difference explains why the same notation means something ornamental in one part and something structural in another, and why a player transcribing between instruments has to decide which they are looking at.

Composers reach for the effect at specific moments and the associations are well established. Sustained shimmering strings under a held harmony signal tension and are the standard film scoring device for approaching danger, used so consistently that the sound is a cue before anything happens on screen. A sudden switch to it in an orchestral passage changes the texture instantly without changing the notes, which is a cheap and effective way to alter atmosphere. On plucked instruments the continuous repetition produces a completely different character, warm and singing rather than agitated, which is why mandolin and classical guitar use it for lyrical melodies. Electronic tremolo applied to a guitar produces a pulsing that sits somewhere between rhythm and timbre and defined the sound of several decades of popular music. The same technique therefore means agitation, lyricism or groove depending entirely on the instrument.

Notation uses slashes through or beside the note stem, with the number of slashes indicating how fast the repetition should be relative to the written value, and three slashes conventionally meaning as fast as possible without a specified rate. Alternation between two notes is written by placing the slashes between them. The system is efficient, since writing out sixty-four repeated notes would be unreadable, and it is imprecise, since the actual speed depends on the instrument, the tempo and the player. Additional words specify the character where it matters. Historical notation used different conventions and reading older scores requires knowing which, since the same symbol has meant measured repetition at a specific rate in some periods and unmeasured shimmer in others, and misreading it produces a performance at the wrong speed entirely.

Tremolo varies loudness by repeating or modulating and vibrato varies pitch, and guitar equipment has the names reversed because of an early manufacturer's error. On plucked and struck instruments the technique exists because notes decay and cannot be held. Notation uses slashes on the stem, which is efficient and leaves the actual speed to the player and the period.