This investigation surveys pertinent literature, from 1917 to 1982 inclusive, regarding artistic vibrato and tremolo in singing. The contents are subdivided into individual investigative reports by various vocal researchers. Due to mounting confusion within the amassed literature, the need for systematic organization and evaluation is evident. Misunderstandings within the context of the literature and misnomers within the terminology require clarification and resolution. The evaluation intends to produce a proper perspective on vibrato and tremolo, eradicating some of the confusion surrounding the terms. Artistic vibrato is recognized as a desirable component in Western vocal music. In contrast, tremolo is deemed a deviant vibrato, i.e., a vibrato which deviates from artistic norms. The study attempts to clarify the distinguishing traits of these two vocal phenomena.