The trill, or oscillation of 2 notes, was a training maneuver featured in nearly all the Old Italian School treatises and writings.

(Russian soprano Antonia Nezhdanova demonstrating trills in W. Taubert’s “The Bird”)

Training manuals and vocalization books of the nineteenth century feature the trill as an important exercise for all voice types. Perhaps no better authority than Pauline Viardot-Garcia (sister of Manuel Garcia, II) can best describe the reason and purpose behind the exercising of the voice in a trill. (Ed. Underlinings are mine)

A precise and detailed indication of the manner of studying the trill has never been possible, for this study must necessarily be modified according to the differences of throats and voices. Nevertheless, since the entire absence of rigidity is the first condition of a well executed trill, I shall endeavor to explain what is, according to my experience, the surest and most rapid means of remedying this most troublesome of all defects: rigidity.

Persons who have not yet studied singing, even children, generally learn the trill more quickly than anything else, for, if they have no acquired qualities, they have not been able to form bad habits of rigidity in the throat. Thus far I have found but few voices ill-adapted to the trill among my pupils, and not one among those who studies I have directed from the very first.

This exercise, whose object is to do away with rigidity, should be studied as follows:

Contrarily to the invariable rule in other cases, take only a weak breath; then, without any force, without the least effort, feebly slurring, with an exaggerated carelessness, without beating time, sing slowly two or three times the first two notes, in order to account for the interval; then all at once hasten the movement as much as possible and soon stop suddenly. Unless one take good care to maintain the distance of the interval by widening it as soon as it is perceived to diminish, it will infallibly close up and will end by becoming a useless tremolo.

As soon as the least rigidity is perceived, whether in the throat, or in the tongue, or in the muscles of the neck or of the nape of the neck, or as soon as we feel that the eyes are becoming fixed, or notice that the head (or the jaw) makes little nervous motions, or that we involuntarily mark the measure, we should break off at the very instant.

This exercise can be made very often during the day, but not for a long time in immediate succession, for in the beginnings the throat easily becomes rigid. It is not necessary to practise it in the chest register, and the interval should not be taken lower than a major third.

This exercise, which, it must be confessed, has very little music in it, is the counterpart of that of the so-called “dead hand,” which pianoforte pupils have to practise, repeatedly striking chords, in order to do away with the rigidity of the wrists.

Viardot-García, Pauline. An hour of study: exercises for the voice. Vol. 2. G. Schirmer, 1897.

So here we have, in its essence, the functional aspect of a vocal trill: the release of rigidity in the vocal mechanism.  A proper trill cannot be performed without complete freedom in the vocal muscles, and because of this, the exercise has untold benefits. We seldom hear a proper trill in 2013, (either on the stage or in voice studios); could this be due to the rigid, over-brusque, muscled voices we hear today? I believe this is so.

Where does the trill stand in modern training?

One of the few authors to write on a version of the trill, as prescribed by Mme Viardot, is W. Stephen Smith. In his book, “The Naked Voice”, he prescribes an exercise he refers to as “The Wobble”.  He states,

When we give up control of the larynx, singing various intervals will feel like an out-of control wobble, so using the term helps conceptualize the sensation of total loss of control, which is, in fact, true freedom. 

[…]

The application of the Wobble is simple. We just alternate between pitches that are four tones apart, first slowly and then quickly. We begin singing [a] on a given pitch and then sing another [a] up a fourth from the first pitch, and then alternate those pitches for four quarter notes, followed by two beats of eight sixteenth notes (also on [a]), ending with a quarter note [a] on the original pitch.

Smith, W. Stephen, and Michael Chipman. The Naked Voice. Oxford University Press, 2007.

How close this description is to the assertions of Pauline Viardot-Garcia!

The trill is a valuable FUNCTIONAL tool for inducing freedom in a voice.  It is a wonderful study in total vocal freedom, and even imperfect attempts at the trill can be beneficial in showing the singer a pathway to ‘letting go’.

Here are the examples of trills over wider intervals from Viardot’s book, “An Hour of Study”: