Vocal registers arise from different vibratory patterns produced by the vocal cords. Research by speech pathologists and some vocal pedagogists has revealed that the vocal cords are capable of producing at least four distinct vibratory forms, although not all persons can produce all of them. The first of these vibratory forms is known as natural or normal voice; another name for it is modal voice, which is widely used in 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 range (although there is some overlap), and its own characteristic sound. Arranged by the pitch ranges covered, vocal fry is the lowest register, modal voice is next, then falsetto, and finally the whistle register.