In speech pathology, the vocal register has three components: a certain vibratory pattern of the vocal folds, a certain series of pitches, and a certain type of sound. Although this view is also adopted by many vocal pedagogists, others define vocal registration more loosely than in the sciences, using the term to denote various theories of how the human voice changes, both subjectively and objectively, as it moves through its pitch range. There are many divergent theories on vocal registers within vocal pedagogy, making the term somewhat confusing and at times controversial within the field of singing. Vocal pedagogists may use the term vocal register to refer to any of the following: