Vibrato as it is used by modern flutists developed in late Nineteenth Century France. In describing their tone they talked more of warmth than vibrato. Listening to Philip Gaubert gives a good understanding of this - one needs to listen closely to hear the quick, narrow pulse. Listen again at 300% slower speed.
Marcel Moyse also followed in this tradition. The vibrato can be studied clearly at 300% slower.
Julius Baker termed this fast narrow vibrato "spinning the sound." Listen to him playing the opening to the second movement of the Debussy Sonata, and the same passage 300% slower.
In the above example notice how the top of each vibrato wave is tuned to the pedal C of the viola.
The listener hears the highest pitch when a note is vibrated. This is the pitch that must be tuned to the accompaniment.
One has only to think of a string player's vibrato movement and hear it slowly. Or listen to a great soprano and hear the vibrato slowed down. I call this incorporating the vibrato into the sound.
Sometimes a flutist will start a note in tune with an accompaniment and then vibrate above that pitch. The "high power" of this effect when produced by James Galway can be analysed in slow motion. In the hands of a less masterful player, particularly if the upward push is greater and slower, the effect on the listener will be sharpness rather than brilliance.
The flutists in the above examples use a vibrato of four pulses at a speed of 92-96 and a width of less than a half step. You may notice that they tend to vibrate evenly and consistently on long notes and not on short notes. You may notice how they tend to make a note end on the upper pitch so that it makes a true legato connection to the following note. When performers vibrate on quick notes there is a tendency for this legato to be broken.
Vibrato speeds above 96 will tend to involve tightness and sound nervous. This is particularly true if combined with a larger width.
Many professional flutists in the early Twentieth Century played without vibrato or with a very quick narrow one as does the English player Robert Murchie in this example. The quivery tremble at faster than 120 is clearly heard when slowed down. Without vibrato at all is Eli Hudson - also slowed.
Narrow vibrato slower than 84 can create a peaceful effect but if it is wide it can tend to intrude on the sound. In my opinion the vibrato in this example of Aurele Nicolet although beautifully controlled draws attention to itself. The combination of slowness with width can be examined in slow motion.
The width of the vibrato pulses can vary from an almost imperceptible pitch variation (the variation is largely intensity) to a full half step. Even beyond this some vibratos are so exaggerated that there is almost silence between the pulses.
Problems and solutions
Many students start each note without any vibrato and then start an upward vibrato. Apart from the effect on the pitch this also inhibits the forward sense of phrasing. Instead start the note at the top of the pitch (in tune with the accompaniment) and vibrate downwards.
Students need to practice with a metronome to first be sure the pulsing is regular. Start practicing at the speed that seems most comfortable and begin to move the metronome toward the range of 84-96 for four pulses. For some students this will mean speeding their normal vibrato; for others slowing it down.
Once control is reached in this tempo range practice setting the metronome on successive speeds from very slow to very fast. Fit an even number of pulses to the beat, from six or even seven for a slow beat to two for a fast one. Then experiment to see whether you can fit two different numbers of pulses into a specific beat. For example put the metronome on 60 and practice both five pulses to the beat and six pulses to the beat.
The width of the vibrato is controlled by the extent to which the glottal (choking) muscle in the throat is exercised. If you have trouble narrowing the width try thinking that you are not vibrating at all, although you feel the pulses in your head. Think of bringing the air right up to the inside of the top lip without involving the throat. Think of blowing the airstream high into one or both cheeks. Feel the vibrato happening of its own accord rather than making it happen.
To practice varying vibrato width try imagining a non-audible vibrato pulse on a sustained note. Then try to make an imperceptible vibrato, making it gradually more noticeable. Keep increasing the width until there seems to be almost silence between the pulses. The goal is to warm the sound gradually, not to have a wide vibrato suddenly apparent.
Ultimately the use of vibrato is an element of artistry and can be varied to color the music. There is a place for all the extremes mentioned above, but their use needs to be both controlled and helpful to the mood of the moment. A faster vibrato sounds more intense than a slow one. A fast and wide vibrato is the most intense. A slow narrow vibrato can sound sensuous. A slow wide vibrato can sound langorous. A fast vibrato that varies only intensity can sound nervous. Above all develop a singing vibrato that is incorporated into your basic sound and does not draw attention to itself.
Listen to some more flutists to see how they approach vibrato.
Jeanne Baxtresser playing Amirov and the same slowed down.
William Bennett playing Saint-Saens and the same slowed down.
Harold Bennett playing Debussy and the same slowed down
André Jaunet playing Pergolesi and the same slowed down.
William Kincaid playing Gluck and the same slowed down.
Joseph Mariano playing Griffes and the same slowed down.
Susan Milan playing Fauré and the same slowed down.
Thomas Nyfenger playing Enesco and the same slowed down.
Jean-Pierre Rampal playing Reinecke and the same slowed down.
Paula Robison playing Hindemith and the same slowed down.
Maurice Sharp playing Griffes and the same slowed down.
Alexa Still playing Foote and the same slowed down.
Ransom Wilson playing Schwantner and the same slowed down.
Carol Wincenc playing Schoenfeld and the same slowed down.
John Wion playing Molique and the same slowed down.
Jacques Zoon playing Wilms and the same slowed down.