Piano touch, hammer action, and string motion
Anders G. Askenfelt, Erik V. Jansson · The Journal of the Acoustical Society of America · 1982
Simultaneous recordings have been made of key velocity, hammer acceleration, and string velocity of two grand pianos. In the experiments it was found that the course of the key velocity varies depending on whether the finger motion is initiated from a position above the key or in contact with the key. The course of the hammer velocity varies somewhat with the key velocity; high key velocity shortens the hammer-key contact time, and low key velocity increases this time. The hammer hits the string approximately at the same moment as the key hits its bottom position. Recordings of string displacement show that in the very low register the starting pulse is considerably shorter than half a period of the string fundamental, in the middle range it is approximately half a period, and in the high register it is considerably longer than half a period and also its amplitude is considerably larger than that of the following half-period.