Vibrato is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms of two factors: the amount of pitch variation ("extent of vibrato") and the speed with which the pitch is varied ("rate of vibrato").^[1]

Vibrato and tremolo

Spectrogram illustrating the difference between tremolo and vibrato.

The terms vibrato and tremolo are sometimes used interchangeably, although the strict definitions of each describe them as separate effects: vibrato is a periodic variation in the pitch (frequency) of a musical note, whereas tremolo usually refers to periodic variations in the volume (amplitude) of a musical note. In practice, it is difficult for a singer or musical instrument player to achieve a pure vibrato or tremolo (where only the pitch or only the volume is varied), and variations in both pitch and volume will often be achieved at the same time. Electronic manipulation or generation of signals makes it easier to achieve or demonstrate pure tremolo and/or vibrato.

There are some instances where one of the terms (vibrato, tremolo) is used to describe the effect normally associated with the other term. For example, vibrato is sometimes referred to as tremolo, notably in referring to the vibrato arm of an electric guitar as a "tremolo arm", which produces variations of pitch. Conversely, the so-called vibrato unit built in to many guitar amplifiers produces what is known as tremolo in all other contexts. See vibrato unit for a detailed discussion of this terminology reversal.

Leslie speaker

A Leslie speaker (best known through its historical and popular association with the Hammond organ) creates vibrato as a byproduct of tremolo production. As a Leslie speaker is moved by the rotating mechanism on which it is mounted, it moves closer to or farther away from any given object (such as a listener's ears) not also mounted on the mechanism. Because amplitude varies directly with sound pressure (A = k₁P) and sound pressure varies directly with distance (P = k₂d), such that amplitude also varies directly with distance (A = k₁(k₂d) = k₁k₂d), the amplitude of the sound as perceived by the listener will be greatest when the speaker is at the point in its rotation closest to the listener and least when the speaker is farthest away. Because the speaker is constantly moving either toward or away from the listener, however, the mechanism's rotation is constantly affecting the listener-perceived sound's wavelength by either "stretching" the wave (increasing wavelength) or "squeezing" it (decreasing wavelength) -- and because frequency, i.e., pitch, is inversely proportional to wavelength, such that increasing wavelength decreases frequency and vice versa, any listener for whom the speaker's motion changes the sound's perceived amplitude (i.e., any listener whose distance from the speaker is changing) must also perceive a change in frequency.

Acoustic basis

The use of vibrato is intended to add warmth to a note. In the case of many string instruments the sound emitted is strongly directional, particularly at high frequencies, and the slight variations in pitch typical of vibrato playing can cause large changes in the directional patterns of the radiated sound.^[2] This can add a shimmer to the sound; with a well-made instrument it may also help a solo player to be heard more clearly when playing with a large orchestra.^[3]

This directional effect is intended to interact with the room acoustics to add interest to the sound, in much the same way as an acoustic guitarist may swing the box around on a final sustain, or the rotating baffle of a Leslie speaker will spin the sound around the room.

Typical rate and extent of vibrato

The rate and extent of the variation in pitch during vibrato is controlled by the performer. The extent of vibrato for solo singers is usually less than a semitone (100 cents) either side of the note, while singers in a choir typically use narrower vibrato with an extent of less than +/- a tenth of a semitone (+/- 10 cents).^[1] Wind and bowed instruments generally use vibratos with an extent of less than +/- half a semitone.^[1]

Vibrato's use in various musical genres

Vibrato is sometimes thought of as an effect added onto the note itself, but in some cases it is so fully a part of the style of the music that it can be very difficult for some performers to play without it. The jazz tenor sax player Coleman Hawkins found he had this difficulty when requested to play a passage both with and without vibrato by the producer of a children's jazz album to demonstrate the difference between the two. Despite his technique, he was unable to play without vibrato. A symphony saxophonist was brought in to play the part.

Many classical musicians, especially singers and string players, have a similar problem. The violinist and teacher Leopold Auer, writing in his book Violin Playing as I Teach It (1920), advised violinists to practise playing completely without vibrato, and to stop playing for a few minutes as soon as they noticed themselves playing with vibrato in order for them to gain complete control over their technique.

In classical music

The use of vibrato in classical music is a matter of some dispute. For much of the 20th century it was used almost continuously in the performance of pieces from all eras from the Baroque onwards, especially by singers and string players. A drastic change in approach cannot be understood wholly without regarding the rise of notionally historically accurate ("period") performance from the 1970s onwards. However, there is no actual proof that singers performed without vibrato in the baroque era. Vocal music of the renaissance is almost never sung with vibrato as a rule, and it seems unlikely it ever was. There are only a few texts from the period on vocal production, but they all condemn excessive use of vibrato. However, it should be understood that "vibrato" occurs over a wide range of intensities: slow, fast, wide, and narrow. Most sources in condemning the practice seem to be referring to a wide, slow, perceptible oscillation in pitch, usually associated with intense emotion, whereas the ideal for modern vibrato, and possibly in earlier times as well, was to imitate the natural timbre of the adult singing voice, from which a measure of vibrato (it has since been shown) is rarely absent.

Leopold Mozart’s Versuch einer gründlichen Violinschule (1756), for example, provides an indication of the state of vibrato in string playing at the end of the baroque period. In it, he concedes that “there are performers who tremble consistently on each note as if they had the permanent fever”, condemning the practice, and suggesting instead that vibrato should be used only on sustained notes and at the ends of phrases when used as an ornament.^[4] This however, does not give anything more than an indication of Mozart's own personal taste, based on the fact that he was an educated late Rococo/Classical composer. Mozart acknowledges the difference between the heavy, ornamental vibrato that he finds objectionable, and a more continuous application of the technique less obtrusively for purposes of improving tone quality (in which case he does not refer to it as "vibrato" or "tremolo" at all; describing it merely an aspect of correct fingering). In this respect he resembles his contemporary, Francesco Geminiani, who advocated using vibrato "as frequently as possible" on short notes for this purpose. Although there is no aural proof, as audio recordings were not around for more than 150 years, that string players in Europe did not use vibrato, its overuse was almost universally condemned by the leading musical authorities of the day.

Certain types of vibrato, then, were seen as an ornament, but this does not mean that it was used sparingly. In wind playing too, it seems that vibrato in music up to the 20th century was seen as an ornament to be used selectively. Martin Agricola writing in his Musica instrumentalis deudch (1529) writes of vibrato in this way. Occasionally, composers up to the baroque period indicated vibrato with a wavy line in the sheet music. Again, this does not suggest that it was not desired for the rest of the piece any more than the infrequent use of the term in 20th-century works suggests that it is not used elsewhere.

In jazz

Most jazz players for the first half of the 20th century used vibrato more or less continuously. Since around the 1950s and the rise of bebop, continuous use of vibrato has largely fallen out of style in favor of more selective use.

In folk

Folk music singers and instrumentalists up to the present day rarely or never use vibrato. It tends only to be used by performers of transcriptions or reworkings of folk music that have been made by composers from a classical, music-school background such as Benjamin Britten or Percy Grainger.

The use of vibrato in some folk music is rare, or at least less pronounced than in other forms of music, although in Eastern European, Balkan, Middle Eastern, or Indian musics, for example, it can be very wide.

In pop

In pop (as opposed to opera), the vibrato usually starts somewhere in the latter part of the note. In the case of some pop balladists, the vibrato can be so wide as to constitute a pronounced wobble, although not as pronounced as that present in some badly trained or over-worked operatic voices. Many singers use pitch correction software in which the effect can be reduced or eliminated as a result of pitch quantization.

Techniques for producing vibrato

Not all instruments can produce vibrato, as some have fixed pitches which cannot be varied by sufficiently small degrees. Most percussion instruments are examples of this, for instance the xylophone.

Keyboard instruments

Some types of organ, however, can produce the effect by altering the pressure of the air passing through the pipes, or by various mechanical devices (see the Hammond or Wurlitzer Organs for example). The clavichord, though technically a fixed-pitch keyboard instrument, is capable of producing a type of vibrato known as Bebung by varying the pressure on the key as the note sounds. Some digital keyboards can produce an electronic vibrato effect, either by pressure on the keys, or by using a joystick or other MIDI controller.

String instruments

The method of producing vibrato on other instruments varies. On string instruments, for example, the finger used to stop the string can be wobbled on the fingerboard, or actually moved up and down the string for a wider vibrato.

Many contemporary string players vary the pitch from below, only up to the nominal note and not above it,^[5] although great violin pedagogues of the past such as Carl Flesch and Joseph Joachim explicitly referred to vibrato as a movement towards the bridge, meaning upwards in pitch,^[6]—and the cellist Diran Alexanian, in his 1922 treatise Traité théorique et pratique du Violoncelle, shows how one should practice vibrato as starting from the note and then moving upwards in a rhythmic motion.^[7] In a 1996 acoustic study by the Acoustical Society of America, along with Wellesley College and the Massachusetts Institute of Technology, found that the perceived pitch of a note with vibrato "is that of its mean", or the middle of the fluctuating pitch.^[8]

The guqin, a Chinese bridgeless zither, has documents describing over 25 different types of vibrato that can be executed. Most peculiar is the vibrato ting yin (literally "still vibrato"); ancient manuals state that the finger on the left hand that is pressing the string should only move or rock ever so slightly so as to alter the pitch minutely, and some manuals say that the finger should not move at all but let the pulse of the finger do the vibrato.

Wide vibrato, as wide as a whole-tone, is commonly used among electric guitar players and adds the signature vocal-like expressiveness to the sound. This effect can be achieved both by the movement of fingers on the fretboard and by the use of a tremolo arm, a lever that adjusts the tension of the strings.

Wind instruments

Players of wind instruments generally create vibrato by modulating their air flow into the instrument. This may be accomplished either through stomach vibrato, the pulsing of the diaphragm slightly up and down, or throat vibrato, a variation of vocal chord tension to manipulate air pressure as singers do. Players of other instruments may employ less common techniques. Saxophonists tend to create vibrato by repeatedly moving their jaw up and down slightly. Clarinet players rarely play with vibrato, but if they do, the saxophone method is common because of the similarity of the saxophone and clarinet mouthpieces and reeds.

Brasses

Brass instrument players may produce vibrato by gently shaking the horn which varies the pressure of the mouthpiece against the lip. This is referred to as hand vibrato, and is more favored in higher brass. Alternatively, the embouchure can be rapidly altered, essentially repeatedly "bending" the note. This is called lip-vibrato, and is probably the most commonly used technique of vibrato on a lower brass instrument.^[9] On a trombone, a player may provide a slightly more pronounced vibrato by gently moving the slide back and forth, centering on one note to give a lyrical effect. Often, this is more of a jazz technique. This is called slide vibrato. In brass playing, diaphragmatic vibrato is possible, but not often preferred.

Auto-vibrato

Some instruments can only be played with constant, mechanical vibrato (or none at all), notably electric organists using a Leslie speaker. Vibrato on the theremin, which is a continuously variable-pitch instrument with no "stops", can range from delicate to extravagant, and often serves to mask the small pitch adjustments that instrument requires.

Sound examples

•  Vibrato, Sound Frequency 500 Hz - Frequency Modulation 50 Hz - Vibrato Frequency 6 Hz (help·info)
•  Tremolo, Sound Frequency 500 Hz - Amplitude Modulation 6 Hz (help·info)
•  Tremolo by beating - Sound Frequencies 500 and 506 Hz, Beat Frequency 6 Hz (help·info)

References

External links

• Vibrato or tremolo? - technical treatment, but accessible to laypersons
• The Vibrato Page - collection of opinions and quotes against vibrato.
• Roger Norrington writing on vibrato - from a conductor's perspective
• David Montgomery: The Vibrato Thing - from a musician's perspective, debunking Norrington and Moens-Haenen
• Punctuating your Lead Guitar with String Vibratos
• Use of Vibrato in Baroque Vocal Music - Historical documentation, brief but clear scientific explanation, and a short bibliography
• David Hurwitz: Vibrato in the Classical Orchestra - latest of three-part essay refuting Norrington and his school; covers the Classical Period
• A riddle over vibrato of clarinet