Loudness control in pianists as exemplified in keystroke force measurements on different touches

The relationship between the key depression force on an upright piano and the level of loudness of a generated tone was examined when pianists hit a force-sensor built-in key with "struck" or "pressed" type of touch. The vertical displacement of the key, and the radiated piano sounds were also recorded. It was found that for both types of touch, simple exponential functions could adequately describe the relation of the force amplitude with the level of the piano tone as well as that of the impulse of the force with the piano tone. The impulse of the force generated before the maximum key depression moment commonly amounted to above 80% of the total impulse produced at the tone below mezzo-forte. It, however, decreased to around 60% at fortissimo, indicating a decrease in the efficiency of the force application for sound production. The two types of touch differed in their force profiles. The struck touch was characterized by a steeper initial force increase with greater fluctuations in the subsequent period than the pressed touch. The struck touch also demonstrated lower maximum force and less impulse at fortissimo. The inter-pianist variation in the force and impulse, and the "finger-noise" are also herein examined.