Analysis of Vocal Imitations of Pitch Trajectories

In this paper, we analyse the pitch trajectories of vocal imitations by non-poor singers. A group of 43 selected singers was asked to vocally imitate a set of stimuli. Five stimulus types were used: a constant pitch (stable), a constant pitch preceded by a pitch glide (head), a constant pitch followed by a pitch glide (tail), a pitch ramp and a pitch with vibrato; with parameters for main pitch, transient length and pitch difference. Two conditions were tested: singing simultaneously with the stimulus, and singing alternately, between repetitions of the stimulus. After automatic pitchtracking and manual checking of the data, we calculated intonation accuracy and precision, and modelled the note trajectories according to the stimulus types. We modelled pitch error with a linear mixed-effects model, and tested factors for significant effects using one-way analysis of variance. The results indicate: (1) Significant factors include stimulus type, main pitch, repetition, condition and musical training background, while order of stimuli, gender and age do not have any significant effect. (2) The ramp, vibrato and tail stimuli have significantly greater absolute pitch errors than the stable and head stimuli. (3) Pitch error shows a small but significant linear trend with pitch difference. (4) Notes with shorter transient duration are more accurate.