vibrato explained
A slight, rapid fluctuation of pitch used to enrich and warm the tone of a sustained note
In Depth
Vibrato is produced differently on each instrument: string players oscillate the left-hand finger; wind players vary the air stream, embouchure, or jaw; singers pulse the larynx or diaphragm. The speed and width of vibrato vary with period, style, and personal taste. In Baroque performance, vibrato was an ornament applied selectively; by the Romantic era, continuous vibrato became the default for strings and voice. The debate over appropriate vibrato is one of the most contentious issues in historical performance practice.
Fritz Kreisler was one of the first violinists to use continuous vibrato as a default, and early critics accused him of playing out of tune because they were unaccustomed to the sound.