Straight and Slide Key Touches Alter the Harmonic Structure of Piano Tones

抄録

This study investigated whether different key-touch motions can systematically alter the harmonic structure of piano tones even when peak sound pressure levels are matched. Two contrasting touch types were compared: a straight touch, in which the fingertip pressed vertically downward from a fixed contact point, and a slide touch, in which the fingertip slid toward the back of the key while depressing it. Piano tones (C4) were recorded from a Yamaha grand piano under tightly controlled peak sound pressure levels. Key displacement was also measured using a laser displacement sensor. Spectral analyses revealed clear and consistent differences in harmonic energy distribution between the two touch types, and these differences persisted for approximately 2 s after onset. Additional muted-string recordings showed that touch-related mechanical noise decayed within about 0.15 s, indicating that the sustained spectral differences were unlikely to be explained solely by touch noise. A two-alternative forced-choice listening experiment with 20 non-musicians further showed that listeners could reliably discriminate the two tone types even when the initial 0.5 s segment was removed. These results suggest that touch-dependent differences can influence the musical sound itself even after touch-related mechanical noise has decayed.