Influence of melodic context on the perception of vocal pitch accuracy

In order to categorize sung performances as “in tune” or “out of tune”, one can measure the deviation between the performance and the musical notation. Depending on the study, a deviation of a semitone (100 cents) or a quartertone (50 cents) is considered as “out of tune”. However, these values are arbitrary and the current study aims to define perceptual thresholds of pitch accuracy in a melodic context.
For this purpose, melodic sequences were manipulated, from “in tune” (deviation of 0 cent) to “out of tune” (10 to 80 cents, in 10 cents steps). In a 2x2x2 design we systematically varied the conditions of: melodies (ascending/descending target-interval), type of errors (interval or tonality deviation), and direction of the deviation (enlargement or compression). The sequences were presented to 30 non-musicians using the method of limits procedure, in a test/retest paradigm. For each condition, they were asked to specify whether the presented singing performances were “in tune” or “out of tune”.
The results showed that participants were consistent in their evaluation between the test and the retest. The pitch accuracy threshold (M = 29 cents, ES = .75) was not influenced by the melody, the type of errors, and the direction of the deviation.
This study highlights the ability of non-musicians to perceive small pitch deviations (less than a quartertone) in a melodic context. This finding elucidates on the concept of pitch accuracy and therefore yields the opportunity to revise objective tools for the evaluation of singer pitch accuracy.