Vibrato is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms of two factors: the amount of pitch variation ("extent of vibrato") and the speed with which the pitch is varied ("rate of vibrato").
Read more about Vibrato: Vibrato and Tremolo, Leslie Speaker, Acoustic Basis, Typical Rate and Extent of Vibrato, Vibrato's Use in Various Musical Genres, Techniques For Producing Vibrato, Sound Examples