Violin vibrato technique and its implication for pitch perception
As the physical models of acoustic instruments improve, there is an ever increase need to model the human being playing the instrument. Vibrato is one of the major factor by which the musicians can make the instrument more expressive.
Various pitch-matching research involving vibrato, including a study using actual string sounds, have shown that listeners hear the center frequency of a vibrato as the main pitch. Yet, the violinists are taught not to make the intended pitch the center of the vibrato motion. They are taught to "vibrate only below and up to the principal tone" (Bang 1923) or that a "vibrato is a rapid alteration of correct and flattened pitch." (Grimson & Forsyth 1923) or told that "a correct vibrato go from pitch to below and backup" (Lucketenberg 1994). This contradiction is studied here.
A preliminary FFT analysis of a violinist over a long period (1-2 seconds) shows that for many of the vibrato notes, the fundamentals are indeed slightly lower. But on hearing the vibrato it sounds to be the intended pitch. A complex interaction between the FM sidebands, phase relation among the partials, and their AM characteristics may be contributing to this phenomena.
Various conservatory-level students and teachers will be sampled at various pitches in a musical context to see if this tendency to play slightly lowered vibrato is common and also listening tests will be performed to identify the pitches of the sampled vibrato notes.