What is Vocal registration ? Pt2

Vocal registration
From highest register to lowest register
Whistle
Falsetto
Modal
Vocal fry

The number of vocal registers
Indiscriminate use of the word register has led to much confusion and controversy about the number of registers in the human voice within vocal pedagogical circles. This controversy does not exist within speech pathology as speech pathologists view vocal registers from a purely physiological standpoint that is concerned with laryngeal function. Various writers concerned with the art of singing state that there are from one to seven registers present. The diversity of opinion in this area is quite wide and there is no one consensus or point of view. Many vocal pedagogists partially blame this confusion on the incorrect use of the terms "chest register" and "head register". These professionals argue that since all registers originate in laryngeal function, it is meaningless to speak of registers being produced in the chest or head. The vibratory sensations which are felt in these areas are resonance phenomena and should be described in terms related to resonance, not to registers. These vocal pedagogists prefer the term "chest voice" and "head voice" over the term register. Many of the problems which people identify as register problems are really problems of resonance adjustment. This helps to explain the multiplicity of registers which some vocal pedagogists advocate. For the purposes of this article, resonance problems are relegated to their own area since their usage here is controversial and without an overall supporting consensus.For more information on resonance see Vocal resonation.
Vocal registers arise from different vibratory patterns produced by the vocal cords. Research by speech pathologists and vocal pedagogists has revelaed that the vocal cords are capable of producing at least four distinct vibratory forms, although all persons cannot produce all of them. The first of these vibratory forms in known as natural or normal voice; another name for it-modal voice- which is currently highly used among both speech pathology and vocal pedagogy publications. In this usage, modal refers to the natural disposition or manner of action of the vocal cords. The other three vibratory forms are known as vocal fry, falsetto, and whistle. Each of these four registers has its own vibratory pattern, its own pitch area (although there is some overlapping), and its own characteristic sound. Arranged by the pitch areas covered, vocal fry is the lowest register, modal voice is next, then falsetto, and finally the whistle register.
The confusion which exists concerning what a register is, and how many registers there are, is due in part to what takes place in the modal register when a person sings from the lowest pitches of that register to the highest pitches. The frequency of vibration of the vocal folds is determined by their length, tension, and mass. As pitch rises, the vocal folds are lengthened, tension increases, and their thickness decreases. In other words, all three of these factors are in a state of flux in the transition from the lowest to the highest tones.
If a singer holds any of these factors constant and interferes with their progressive state of change, his laryngeal function tends to become static and eventually breaks occur, with obvious changes of tone quality. These break are often identified as register boundaries or as transition areas between registers. Many pedagogists disagree with this distinction of boundaries blaming such breaks on vocal problems which have been created by a static laryngeal adjustment that does not permit the necessary changes to take place. This difference of opinion has effected the different views on vocal registration.