Acoustic cues of keyboard mechanics enable auditory localization of upright piano tones

Piano tone localization at the performer's listening point is a multisensory process involving audition, vision, and upper limb proprioception. The consequent representation of the auditory scene, especially in experienced pianists, is likely also influenced by their memory about the instrument keyboard. Disambiguating such components is not obvious, and first requires an analysis of the acoustic tone localization process to assess the role of auditory feedback in forming this scene. This analysis is complicated by the acoustic behavior of the piano, which does not guarantee the activation of the auditory precedence effect during a tone attack, nor can it provide robust interaural differences during the subsequent free evolution of the sound. In a tone localization task using a Disklavier upright piano (which can be operated remotely and configured to have its hammers hit a damper instead of producing a tone), twenty-three expert musicians, including pianists, successfully recognized the angular position of seven evenly distributed notes across the keyboard. The experiment involved listening to either full piano tones or just the key mechanical noise, with no additional feedback from other senses. This result suggests that the key mechanical noise alone activated the localization process without support from vision and/or limb proprioception. Since the same noise is present in the onset of the full tones, the key mechanics of our piano created a touch precursor in such tones that may be responsible of their correct angular localization by means of the auditory precedence effect. However, the significance of pitch cues arriving at a listener after the touch precursor was not measured when full tones were presented. As these cues characterize a note and, hence, the corresponding key position comprehensively, an open question remains regarding the contribution of pianists' spatial memory of the instrument keyboard to tone localization.