Five Kinds of Vibrato

Wikipedia gives a pretty decent introduction to the musical technique of vibrato:
Vibrato (Italian, from past participle of "vibrare", to vibrate) 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").
In singing it can occur spontaneously through variations in the larynx. The vibrato of a string instrument and wind instrument is an imitation of that vocal function.
I could quibble with some of that, of course. Vibrato does not have to be and often isn't all that "regular." One frequently changes the pace of vibrato for musical effect. Vibrato is used more in some genres than others. My mother, for example, an old-time Canadian fiddler, never used vibrato and in fact, did not know how to do vibrato, or at least claimed not to. Classical violinists typically use vibrato in varying amounts depending on the era and style of the piece in question, less in Baroque music, more in Romantic music--but there are lots of ongoing controversies about it.

I want to talk about vibrato on the guitar as that is the instrument I am most familiar with. Correct me if I am wrong, bowed instrument players, but I believe that vibrato on the violin and similar instruments is produced by rolling back and forth on the ball of the finger stopping the note on the fingerboard? As there are no frets, this produces a fluctuation in the pitch, both above and below the "correct" pitch. What do gamba players do, I wonder, or do they just avoid vibrato?

In any case, rolling around on the ball of your fingertip does not do much on fretted instruments as the location of the fret fixes the pitch of the note. So what do guitarists do? It varies according to the type of guitar and genre. Here, for example, is an excellent discussion of how blues guitarists create vibrato:

You get the essence of it in the first minute from the great authority, B. B. King! I played electric blues guitar for several years when I was young, but for the life of me I can't actually recall how I did vibrato. Bending notes, sure, but vibrato? As B. B. hints at in the clip, his method only really produces a vibrato between the pitch and slightly above the pitch. It is a kind of heightened expression that, "shimmers." Another famous practitioner is Eric Clapton and he talks about it in an interview somewhere.

Bending notes is quite different on the classical guitar as opposed to the steel string one. You have to work a lot harder bending notes on nylon strings and it is never as effective. As the blues vibrato is basically a kind of note-bending, pushing the string to one side, it is not a good technique on classical guitar. So what do we do instead? On steel string guitars, you bend notes and do vibrato by increasing the string tension by pushing the string to one side. You are basically raising the pitch by increasing the tension. On classical guitar, you do it slightly differently. You also increase the tension but by pulling on the string laterally instead of pushing it to one side. Imagine you are stopping a note on, say, the fifth or seventh fret. If you move your arm away from your body while keeping the pressure on the string you will raise the tension and hence the pitch. If you move your arm toward your body you will be lowering the tension of the vibrating part of the string and therefore lowering the pitch. It is a kind of a see-saw: as you push or pull the string, the tension raises on one side and lowers on the other. This gives you a vibrato on both sides of the "correct" pitch, as with the violin.

The hitch is that this only works if you have sufficient string length on either side. Once you get down to the end of the fingerboard close to the tuners, it won't work because you have almost no string length on the non-vibrating part of the string. So what do you do there? Essentially a variant of what B. B. is showing in the clip: you let your thumb loose and pull the string to one side with a wavering motion of the hand. It works well enough, but not as satisfactory as the vibrato higher on the fingerboard. For that kind, the closer you are to the middle of the string, the easier it is.

When I was a young student in Spain, studying with José Tomás, I remember hearing another student say that Tomás taught that there were five kinds of vibrato. We never got into that in any of my lessons and it never came up in the master class so I don't know what the "five kinds" actually were. I could speculate a bit...

In a lute treatise somewhere the author mentions an odd and very subtle kind of vibrato that is actually not a vibrato at all, but a kind of tremolo (a quickly repeated note). While holding a note with the index finger of the left hand, you could, very gently, tap several times on the vibrating string close to the end being stopped. If done lightly and carefully enough it will result in a kind of fluttering note. This is used for expressive effect in 17th century lute music.

Ok, that, with the two before, gives us three kinds of vibrato. What do you do if you have an open string and want to do vibrato? I suppose that an electric guitarist might use the whammy bar, push on the neck, or just fiddle with the string after the nut, but those are not going to work on a classical guitar. What you can do is shake the whole guitar. While not hugely effective, it will do something.

Last but not least, if all else fails, you just shake your head!

Q. E. D. Five kinds of vibrato.

The Prelude No. 1 by Villa-Lobos is particularly well suited to the use of vibrato because of the way the melody is distributed over the strings. Here is a performance by John Williams (sorry about the sound quality, but the vibrato is pretty evident):

Here is Andrés Segovia with a more variable vibrato:

Source: themusicsalon

Five Kinds of Vibrato