A speed detecting apparatus for a keyboard musical instrument is provided
for accurately detecting the speed of bivotal movements of a hammer and a
key even if a shutter implies errors in its attachment, without affected
by such errors. The speed detecting apparatus for a keyboard musical
instrument comprises a pivotable key, a hammer pivotably supported by a
fulcrum and configured to pivotally move in association with a pivotal
movement of the key, a shutter integrally attached to the hammer, a
plurality of detectors, each having a light emitter and a light receiver
for receiving light emitted from the light emitter, arranged on one and
the other sides of the pivotal movement path of the shutter, and a CPU
for detecting a pivot speed of the hammer in response to timings at which
the shutter opens and closes the light paths of the light of the
plurality of detectors when the hammer pivotally moves. The plurality of
detectors have detection points on respective light paths of the light
from the light emitters, and are arranged such that the detection points
are positioned on an arc centered at the fulcrum of the hammer.