Good vibrato
The "vibrato" playing technique, in which the finger stopping the string is cyclically rocked backwards and forwards, periodically changes the pitch of a note. (a) A one second section of a single bowed note played on a Stradivarius violin, showing the periodic changes in amplitude that are also produced with the use of vibrato. (b) Shorter time intervals, illustrating the periodic changes in waveform at the maxima and minima of the amplitude envelope. (c) The associated periodic changes in the amplitudes of the Fourier components. The yellow band in (a) indicates the time interval used to extract the components.