Rhythmic Aspects of Vibrato

Vibrato, the periodic fluctuations of pitch, amplitude and/or timbre, is an important expressive component of musical performances, especially for singers and string players. Next to measuring its characteristics in isolation we believe it is important to relate it to other temporal aspects of performance (global tempo, expressive timing, rhythmic structure), especially since we have discovered that some intriguing hypotheses about such relationships exist in the literature and in the intuitive knowledge of musicians. In this paper we will focus mainly on pitch-vibrato. We will describe an experimental methodology (including ways to extract fundamental pitch from audio data) which was developed to check various hypotheses. Experiments were conducted using a fragment of the "Cygne" piece of Saint-Saens for five different instruments (violin, cello, tenor, theremin, oboe) in different tempi. The questions addressed are the following: Is vibrato rate adapted to tempo; is vibrato phase adapted to the timing of the end of the note; how is the vibrato contour adapted to note duration; are vibrato cycles somehow synchronized to the pulse at a small metrical level? Results will be presented that lead to answers to these questions.