Press a key and its damper lifts, allowing the struck string to vibrate. Releasing the key normally returns the damper and absorbs energy. The right pedal raises the dampers together, so released notes may continue. They still decay: a pedal cannot add energy to a string indefinitely. Some high treble strings have no dampers. In this laboratory every displayed note uses a simplified controllable damping model.

Begin with the same C major chord at 0%, 50% and 100%. Release the keys and compare how quickly the trails fade. Here depth changes the modeled damping continuously. Real instruments have a travel range before dampers lift, different contact points and different responses by register. Fifty percent here is an educational parameter, not a calibration of a physical pedal. Try a shallow depth to shorten the old harmony while retaining a connected phrase.

Hold C4, engage the middle pedal, then release C4. Play E4 and release it. Only C4 is captured by sostenuto; E4 follows the normal damper behavior. Switch the right pedal off for this experiment or it will sustain both notes and mask the difference. Repeated strikes of the same pitch are tracked as separate voices, while the sostenuto latch records the voices already held when engaged.

On a grand piano the left pedal shifts the action, changing how hammers meet strings and felt. Its effect depends on construction and register. Here the soft pedal reduces upper partials and level as an approximation of a softer attack. It does not simulate moving hammers. Many uprights move the hammers closer to the strings instead; their middle pedal may also have a different function.

To connect two harmonies, play the new chord and then release the old pedal promptly, depressing it again once the unwanted sound clears. This is often called syncopated or legato pedaling. In the collision lab, a negative timing value clears before the second chord, zero clears at its onset and a positive value clears after it. Compare an audible gap with an audible blur. A useful choice depends on tempo, articulation, instrument and room.

Sustain describes the continuing vibration of the instrument. Sympathetic resonance occurs when other strings respond to related frequencies. Room reverberation consists of reflections after sound leaves the instrument. This version uses additive synthesized piano-like tones and controllable damping; its optional resonance is a quiet harmonic layer, and its optional room tail uses a synthetic impulse response. Neither is a measured piano or room model. The chart shows an eight-second history of modeled note envelopes, not a microphone spectrum. Model energy is an envelope-based activity index, not measured acoustic power.