For both physiological and acoustic reasons, ‘false’ tonal qualities, as they apply to females, occur within the same limited pitch range as those of their male counterparts. Another factor to be considered is that women do not undergo a voice change at puberty and, as a result, rarely experience a noticeable separation of the voice into two parts. Since singing requires the engagement of both the ‘false’ and the natural voices, female vocalists enjoy a distinct technical advantage over male vocalists. At a very young age, females with a talent for singing intuitively tend to combine the two registers. Consequently, their mechanical status leaves them in a condition where they are ready to sing.
For males, the integration of the falsetto with the chest voice presents a genuine difficulty. Legitimate voice categories aside, certain types of ‘false’ tone qualities will sometimes include a pitch range of at least two octaves (a coordination observable in the technique employed by the countertenor). Nevertheless, this type of register integration represents only a quasi-legitimate or incomplete tonal quality, due to a deficiency of vocalis tension. Consequently, this coordinative arrangement merely indicates one among many phases of the integrative potential involving the falsetto and the chest voice.
At the outer extremes of the vocal pitch range potential lie two characteristically different tonal qualities. The first is identified with the altissimo notes of the coloratura, often referred to as a flute voice or whistle tones. With notes sung in altissimo, the vocal folds become fully approximated through a dampening process. This condition seals the glottis and prevents all but a small elliptical opening, positioned in the anterior portion of the vocal folds, from vibrating.
The second quality to be considered is located at the lowest extreme of both the male and female pitch ranges and is referred to as vocal fry or a pulse register. With this sound, the arytenoid system is functioning without cricothyroid opposition, causing the vocal folds to present a short, stubby vibrating surface capable of functioning only in a state of extreme relaxation. Although this tone quality possesses no legitimacy due to an absence of both a fixed periodicity, a discernable vowel quality and vibrato, it is occasionally useful when attempts are made to correct problems associated with throat constriction.
As for the head voice, it differs in all respects from sounds produced in altissimo in that the vocal folds are not dampened, but continue to vibrate along their outer edges and throughout their full length. At the upper end of its pitch range, head voice qualities terminate at high B-Flat. This terminal point applies to both male and female vocalists, even though their natural pitch ranges are located an octave apart. Within its lower extension, head voice mechanics are more complex, being dependent on the development of the chest voice and the extent to which the cricothyroids remain active.
Simply stated, all voice qualities are formed out of some combination of the chest voice and the falsetto. Consequently, a head voice may be said to make its appearance as a result of tension distributed between the cricothyroids and the arytenoids, where cricothyroid tension (falsetto) becomes more active as the pitch ascends, while by contrast arytenoid tension (chest voice), particularly the vocalis, becomes increasingly active as the pitch range continues its descent. At this juncture, it is important to recall van den Berg’s concept relating to tonal mixtures.
Reid, Cornelius L. Vocal Mechanics and the Cultivation of Listening Skills.