Vocal register
A vocal register in the human voice is a particular series of tones, produced in the same vibratory pattern of the vocal folds, and possessing the same quality. Registers originate in laryngeal function. They occur because the vocal folds are capable of producing several different vibratory patterns. Each of these vibratory patterns appears within a particular range of pitches and produces certain characteristic sounds. The term register can be somewhat confusing at it encompasses several aspects of the human voice. The term register can be used to refer to any of the following:
- A particular part of the vocal range such as the upper, middle, or lower registers.
- A resonance area such as chest voice or head voice.
- A phonatory process
- A certain vocal timbre
- A region of the voice which is defined or delimited by vocal breaks.
- A subset of a language used for a particular purpose or in a particular social setting.
In linguistics, a register language is a language which combines tone and vowel phonation into a single phonological system.
Within speech pathology, the term vocal register has three constituent elements: a certain vibratory pattern of the vocal folds, a certain series of pitches, and a certain type of sound. This view is also adopted by many vocal pedagogists.

# 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.
One prevailing practice within vocal pedagogy is to divide both men and women's voices into three registers. Men's voices are designated "chest," "head," and "falsetto" and woman's voices are "chest," "middle," and "head." This way of classifying registers, however, is not universally accepted. 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 terms "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 revealed 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. The distinct change or break between registers is called a passaggio or a ponticello. Vocal pedagogists teach that with study a singer can move effortlessly from one register to the other with ease and consistent tone. Registers can even overlap while singing. Teachers who like to use this theory of "blending registers" usually help students through the "passage" from one register to another by hiding their "lift" (where the voice changes).
However, 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.

# Vocal fry register
The vocal fry register is the lowest vocal register and is produced through a loose glottal closure which will permit air to bubble through with a popping or rattling sound of a very low frequency. The chief use of vocal fry in singing is to obtain pitches of very low frequency which are not available in modal voice. This register may be used therapeutically to improve the lower part of the modal register. This register is not used that often in singing, but male quartet pieces, male Russian choral pieces, and certain styles of folk music for both men and women have been known to do so.

# Modal voice register
The modal voice is the usual register for speaking and singing, and the vast majority of both are done in this register. As pitch rises in this register, the vocal folds are lengthened, tension increases, and their edges become thinner. A well-trained singer or speaker can phonate two octaves or more in the modal register with consistent production, beauty of tone, dynamic variety, and vocal freedom. This is possible only if the singer or speaker avoids static laryngeal adjustments and allows the progression from the bottom to the top of the register to be a carefully graduated continuum of readjustments.

# Falsetto register
The falsetto register lies above the modal voice register and overlaps the modal register by approximately one octave. The characteristic sound of falsetto is inherently breathy and flute-like with few overtones present. Both men and women can phonate in the falsetto register. The essential difference between the modal and falsetto registers lies in the amount and type of vocal cord involvement. The falsetto voice is produced by the vibration of the ligamentous edges of the vocal cords, in whole or in part, and the main body of the fold is more or less relaxed. In contrast, the modal voice involves the whole vocal cord with the glottis opening at the bottom first and then at the top. The falsetto voice is also more limited in dynamic variation and tone quality than the modal voice.

# Whistle register
The whistle register is the highest register of the human voice. The whistle register is so called because the timbre of the notes that are produced from this register are similar to that of a whistle or the upper notes of a flute, whereas the modal register tends to have a warmer, less shrill timbre. Women of all voice types can use the whistle register. With proper vocal training, it is possible for most women to develop this part of the voice, but some women are unable to do so. Children can also phonate in the whistle register and men can as well in very rare instances.