vibrato

Terminology

History

Descriptions of what would now be characterised as vibrato go back to the 16th century. However, no evidence exists of authors using vibrato before the 19th century. Instead, authors used various descriptive terms interchangeably, including tremolo, bebung, and tremblement, and descriptions such as wavering, shake and trillo. These “terminological uncertainties” continue to pervade modern definitions of vibrato.

Vibrato and tremolo

The terms vibrato and tremolo are sometimes used interchangeably, although (in the classical world) they are properly defined as separate effects. Vibrato is defined as a periodic variation in the pitch (frequency) of a musical note that is perceived as one fundamental frequency. Tremolo, on the other hand, is defined as a fast repetition of the same note (usually a semiquaver) or alternation between two notes, especially on instruments which do not have the ability of producing long sustained notes, such as the guitar (for instance tremolo picking).

Human perception

Currently, the leading understanding is that when vibrato is utilised, listeners are able to focus on the average pitch and hear it as a single fundamental as opposed to the alternation between two different fundamental frequencies. Carl Seashore (1967) conducted the first comprehensive studies on perceptions of vibrato in the context of classically trained singers, finding some individuals are 50-100 times more perceptive of the presence of vibrato than individuals with the least ability and that “much of the most beautiful vibrato is below the threshold for vibrato hearing and is perceived merely as tone quality.” This conclusion was confirmed by William Vennard (1967) who notes that the listener hears only the average pitch, and the fluctuation is interpreted as enhanced tonal quality.

In practice, it is difficult for a singer or musical instrument player to achieve only pitch vibrato (where only the pitch 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 or vibrato.

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. 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.

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 extent of vibrato

The 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) either side. Wind and bowed instruments generally use vibratos with an extent of less than half a semitone either side.

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 Leonard Bernstein when producing his record album "What is Jazz" to demonstrate the difference between the two. Despite his technique, he was unable to play without vibrato. The featured saxophonist in Benny Goodman's Orchestra, George Auld, 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.

The rise of notionally historically informed ("period") performance from the 1970s onwards has dramatically changed its use, especially in music of the Baroque and Classical eras. However, there is no actual proof that singers performed without vibrato in the baroque era. Notably, composer Lodovico Zacconi advocated that vibrato "ought always to be used".

Vocal music of the renaissance is almost never sung with vibrato as a rule, and it seems unlikely it ever was; 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. 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 as 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.

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 in the North American and Western European traditions rarely use vibrato, reserving it for occasional ornamentation. It also tends 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. Vibrato of varying widths and speeds may be used in folk music traditions from other regions, such as Eastern Europe, the Balkans, the Middle East, East Asia, or India.

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 operatic voices. Many singers use pitch correction software in which the effect can be reduced or eliminated.

Techniques for producing vibrato

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

Singing

There are three different voice vibrato processes that occur in different parts of the vocal tract. Peter-Michael Fischer has vibrato types defined by place of production:

The vocalis muscle vibrates at a frequency of 6.5 to 8 Hz.

The diaphragm vibrates at a frequency below 5 Hz vibrato

A combination of the two, resulting in a vibrato whose frequency is between 5 and 6.5 Hz vibrato. Fischer writes:

"This combination is relatively stable in the most beautiful voices. An important feature is that the partial functions can appear during the song as "accents": In the context of the presentation expressive wave dominates respirativa, lyrical character, but in an accelerated, or glottis wave, hard feature heroic, but in a slow way."Some studies have shown that vibrato is the result of a neuromuscular tremor in the vocal folds. In 1922, Max Schoen was the first to make the comparison of vibrato to a tremor due to the following similarities:

Vibrato and tremors have a change in amplitude

Both occur when the muscles are under strain

Neither are under the automatic control of the person

Vibrato and tremors occur at half the rate of normal muscular discharge

Keyboard instruments

Some types of organ can produce vibrato 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, 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,—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. 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.

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 vibrato tailpiece, a lever that adjusts the tension of the strings.

Some violinists, like Leonidas Kavakos, use bow vibrato by moving the right hand up and down slightly to change the angle and pressure of the bow and thus oscillate the pitch and intensity of a note. The first known description of this technique on violin was by Francesco Geminiani. This technique was not limited to violin but was known to players of all string instruments in Italy, France, Germany, and England during the Baroque era. Sylvestro Ganassi dal Fontego is known to have described this technique for the viol da gamba as early as the 16th century.

Woodwind

Players of woodwind 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 cord tension to manipulate air pressure as singers do. Players of other instruments may employ less common techniques. Although saxophonists and clarinetists can also use airflow, it is more common for them to create vibrato by repeatedly moving their jaw up and down slightly. However classical clarinetists rarely play with vibrato.

Brass

Brass instrument players can produce vibrato by repeatedly and rapidly altering the embouchure, or use and shaping of the lips and facial muscles, 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. It is also known to give the best sound and timbre on a brass instrument and is encouraged in upper-level or militaristic style brass ensembles.

Players may also produce vibrato by gently shaking the horn which varies the pressure of the mouthpiece against the lip. This is referred to as hand vibrato. It is more favored in higher brass, but does not possess the same sound quality as lip-vibrato and at upper levels and can be viewed as a technical mistake, most notable in military style brass training.

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, and is called slide vibrato. In brass playing, diaphragmatic vibrato is possible, but is viewed as an immature technique by collegiate or professional brass players as this technique interferes with proper airflow from the lungs to the instrument. The use of diaphragmatic vibrato in a brass setting is detrimental to the sound and stamina that a brass player can produce, and so is strongly discouraged at any level of musical training.

Auto-vibrato

Some instruments can be played only with constant, mechanical vibrato (or none at all). This effect is notable in electric organists using a Leslie speaker, the most popular of which use a two-speed vibrato; a degree of expression is gained from the acceleration between speeds. 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.

Some manufacturers also build vibrato effect pedals that imitate the natural vibrato but can also produce much faster speeds. The vibrato effect is close to a chorus effect.

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.