Pedal knock
A pedal knock is a percussive effect produced with the pedals.
Production
The pedal mechanism has a powerful spring that forces the pedals upwards. If a pedal is released from its slot suddenly, it knocks against the wood of the pedal slot and creates a pedal knock. This effect should be used sparingly, since it is not very friendly to the mechanics of the instrument.
Sound
The sound of a pedal knock is a wooden percussive sound combined with the of the pitch of the strings that the pedal, used to produce the knock, controls. If, for example, a pedal knock is performed by knocking the C-pedal from the C-natural to the C-flat position, the sound of the tuning discs hitting all the C-flat strings will be heard in combination with the knock.
Notation
A verbal explanation is necessary. The rhythm of the pedal knock should be notated with note beams below the two staves. Pedal indications replace the noteheads.
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Pedal knock.
Range
All the pedals can be knocked upwards. That is from the sharp position to the natural position or from the natural position to the flat position.