Spontaneous Formant Tracking: A point of logic Part 2

The C4 to C5 region is of particular interest to baritones, tenors and women. Before we continue with formant tracking with respect to these voice types, it is worthwhile to outline once again certain basics:

1. Definition: Formants are acoustic frequencies bands covering 30-50 Hz of acoustic space, which, depending on their range, define what we hear as vowels.

2. The vocal tract works better when its reactance is inertial. Simply put, this inertial state of the vocal tract helps maintain efficiency at the glottis even when the folds barely touch. This inertial state depends in large part upon formant tracking. The vocal tract reactance is inertial when the formant is above the corresponding harmonic of the standing wave (fundamental pitch and all its harmonics is referred to as the standing wave). We have our good friend, Martin Berggren to thank for this important detail.


3. Four Rules for Modifying Vowels

A. All formant frequencies decrease uniformly as the length of the vocal tract increases

The vocal tract length increases when the larynx lowers.

B. All formant frequencies decrease uniformly with lip rounding and increase with lip spreading.

Lip rounding and lip trumpeting have the same effect (see details on the NCVS page)

C. A mouth constriction lowers the first formant and raises the second formant.

This includes the raising of the tongue principally as in going from the [a] to the [i] vowel whereby the space below the tongue increases (lowering the pitch. Larger spaces have lower pitch) and the space above decreases (raising the pitch. Smaller spaces have higher pitch).

D. A pharyngeal constriction raises the first formant and lowers the second formant.

The reverse of letter C.

In order to follow these rules, we must establish what the default position of the vocal tract should be. I proceed from the following:

The larynx cannot fall to its naturally low position without the jaw being released. The laryngeal position that produces accurately resonance notes in the speaking range (male between 110 and 150 Hz and women between 220 and 260 Hz) should be the default. Therefore:

1. The larynx should maintain that basic low position.
2. The jaw should always return to the [a] position and the tongue and lips should articulate for all changes (consonants and vowels).

If the jaw had to close for vowels and the larynx had to rise, the variables would be too many and since both would narrow and shorten the larynx, the voice would have a thinner quality.

The key to good resonance is establishing healthy phonation and a “natural” resonance space. By natural I mean that the most comfortable laryngeal level must be accomplished. It is just as unproductive to sing with a depressed larynx (forced too low by tongue depression) as it is to sing with a raised larynx (usually from pressed voice, i.e. excessive medial pressure resulting from inadequate sub-glottal pressure).

Assuming that phonation is normal, the resonance strategy should happen as follows:

Modify the vowel as close as possible to the given vowel while tracking the appropriate formant that would render the vocal tract inertial.

1. It is important to figure out which formant (first or second) is the easiest to tract (i.e.
without raising the larynx and requiring the least migration from the given vowel. There
are two reasons for maintaining a naturally low larynx: A) a long vocal tract tends to be more
inertial. B) A longer vocal tract reinforces lower partials, necessary for balance of chiaroscuro
by not losing the natural darker colors of the voice (particularly important for voice types
requiring more dramatic colors).

2. The frequency range of the formant must be above the respective harmonic in order
for the vocal tract to be inertial.

Following these basic principles, the rest becomes a matter of logic. It is also important to understand that the other three upper vowel formants can also have a profound influence. By concentrating on the first two formants (because we have definite information on what influences them) we can accomplish the inertial state that we refer to as “resonant.” Once the singer becomes familiar with the feeling, it becomes easy to track it. Habits begin to form and the process of vowel modification (resonance tracking or formant tracking) becomes practically an instinctive one. This is the goal! The science only gives us a path to experiencing what true resonance is. The refined product is a personal experience and should seem quite natural in the end.

Looking at the /a/ formant chart for C4-B4, we can make some clear decisions relative to the lower passaggio and middle range of women and the middle to high range of men. What is difficult to understand sometimes is that the acoustic choices can be the same for baritone and tenor or soprano and mezzo in the Eb4 to G4 range. A tenor is perfectly capable of tracking F2 on Eb4 for the /a/ vowel. However, the modification would sound extreme because the voice does not sound very stressed on Eb4. The operatic ear accepts vowel modification where the longitudinal tension (tension along their length) on the folds is high. It is perceived that a modification is made to relieve excessive tension (good formant tracking does). A speech-like (F1) non-resonant Eb4 in the tenor voice may sound more “natural” to the average listener than a covered (F2) resonant version because the F2 version requires too much vowel modification for a note that is easy for that voice type. The same note sung covered by an baritone or bass sounds acceptable to the traditional operatic ear. The same may be unacceptable to a musical theater audience who expects speech-like vowels throughout the range. The most important fact we should know relative to resonance strategy is the following:

Although formant frequencies in the F1 region coincide with the lower modal voice (vocalis-dominant) of the male singer and F2 frequencies with the upper modal voice (CT-dominant) in traditional classical singing, formant choices are not absolute. They depend greatly upon genre and style. It is crucial that we do not make the error of making resonance tracking the magic pill for vocal imbalance. Vocal imbalances have a muscular component that is quite independent of acoustic strategy. When the muscular aspect is correct, good acoustic strategy can have a substantial refining effect. The same can be said relative to the female acoustic passaggi.

In the modal range (vocalis and CT both active; what we call the real voice) we deal with a two register muscular modal distinguished by vocalis-dominance on the lower end and CT-dominance in the other. Both male and female voices behave this way, with approximately a one-octave differential between bass and contralto, baritone and mezzo, and tenor and soprano respectively. The modal range covers a little more than two octaves for each voice type. F1 dominates approximately in the lower three-fourths of the male range in the operatic context and F2 takes over in the upper one fourth. For tenors the ratio might be two thirds to one third. In the female voice the ratio is more complex. Because vowel formants are pitch-dependent, there are two formant changes in the female modal range. Roughly one fourth F1-dominance in the chest range, two fourths in the middle range and one fourth in the head range. In short, the male and female voice behave the same muscularly but radically different acoustically because of the octave differential.

This installment Spontaneous Formant Tracking has been long coming, and so I will publish it. The third installment will follow and will address specific strategies for each voice type. I would like YOUR help in the third installment. Please send me requests relative to specific arias or songs that give you trouble, or that you feel could be better addressed. I will analyze the situation and find solutions based on the premises we discuss here. In fact, I would be interested in clips of you singing the phrase in question. I will analyze it acoustically and consider muscular balance as well. I will send you recommendations and see what happens afterwards. I think this would help us all understand the issues we are dealing with.

Happy singing and Happy Holloween!

© 10/31/2008