This weekend in lessons, I spent time with students talking about the idea of the singing voice as comparable to a stringed instrument. For example, the lowest tones of the voice are like the lowest string of a violin, thick; the upper range is like that of the top string; thinner.

We can get into trouble when we try to achieve higher pitches on lower strings. This is the phenomenon of taking the chest register over the break, when the larynx rises and the vowel begins to spread or ‘go horizontal.’ The violin string WILL eventually break, or the player will ‘run out of room.’ The important thing is to change to a thinner string upon ascent in order for the voice to be ‘functionally balanced.’

Imagine how excited I was to find this correlated by Cornelius Reid this morning, when he wrote the following:

Adjustments of the laryngeal musculature made to accommodate varying pitch levels must conform to the known laws of physics if the mechanism is to function properly. To quote Sir James Jeans:

1. When a string and its tension remain unaltered, but the length is varied, the period of the vibration is proportional to the length.
2. When a string and its length remain unaltered, but its tension is varied, the period of vibration is proportional to the square root of the tension.
3. For different strings of the same length and tension, the period of vibration (frequency) is proportional to the square root of the weight of the string.

Since the vibratory pattern of the vocal folds is governed by these same laws, their length, tension and mass must vary with each change in pitch, the dimensions ranging from short and bulky for the lowest pitch range, longer and somewhat thinner for the mid-tonal voice range, and progressively shorter and thinner for the upper extension. As is true of members of the violin family, where identical pitches can be played on different strings, a number of pitches within the tonal compass can likewise be sung with the conformation of the vocal folds set in a variety of ways.

Whether it be a violin string or the vocal folds, tension on a vibrator is regulated by opposing forces. Unlike the violin where the tuning peg is the sole regulatory mechanism, the vocal folds can be drawn into tension in a variety of ways, 1) by the cricothyroids acting alone (to produce a falsetto); 2) by the arytenoids acting alone (to produce the chest register); and 3) by the coordinate activity of both muscle systems. When the first two options are in effect, the pitch range will be restricted to those limits shown in Figure 1. It is not the limits that determine a register, however, but the type of muscular activity that imposes those limits.

A register, therefore, is neither exclusively pitch related nor a pitch range (although its parameters are fixed because of the limitations of frequency relative to the length and thickness of the vocal folds), nor is it a special kind of vocal fold conformation (a determinant of frequency), but a condition which finds either one of two muscle systems drawing the into tension functioning in relative isolation. Consequently, pitch is not the factor in registration, but one element, which, in conjunction with intensity, causes the tensor mechanisms that adjust the vocal folds to participate in a suitable manner. The key factor in registration is the ratio of tension shared between these two mechanisms.

Reid, Cornelius L. Essays on the Nature of Singing. Recital Publications, 1992.