Piano Sustained Note Decay Calculator

Piano note decay: rule and example

When a piano string vibrates freely, the sound dies away exponentially: A(t) = A₀ · e^(-t / τ). The audible length of a note is usually given as the time it takes for the amplitude to fall by about 60 dB (RT60). Bass strings carry more inertia and damp themselves less, so they ring longer. With the sustain pedal held, A0 (27.5 Hz) on a concert grand keeps going for roughly 40 s. By contrast A4 (440 Hz) in the middle holds about 10 s, and the bright treble A7 (3520 Hz) is gone in 3 s. The soundboard pushes those high frequencies out into the room very quickly, which is why they fade first.

Context and applications

Composers writing for solo piano reach for the bass register when they want a sustained pad sitting under a melody that keeps moving. If you know how long a low chord actually lasts, you avoid voicings that have already faded by the time the harmony changes. Technicians voicing a Steinway D work hard to keep the decay even across the transitions in the stringing (plain-wound to wound, bichord to trichord). And MIDI instruments like the Yamaha Disklavier store a separate decay curve for each pitch, so when it plays back through the real soundboard the result lines up with what was recorded.

FAQ

What does the sustain pedal change? It raises every damper at once, so neighbouring strings are free to ring in sympathy. The effective τ goes up because you're no longer bleeding energy into the dampers, and on top of that the listener picks up the resonance from those nearby strings.

And the sustenuto pedal (middle)? It sustains only the notes you were already holding down at the moment you press it, while everything else stays damped. That lets you hold a pedal point without smearing the rest of the texture.

Why does the treble die so fast? Short, light strings just don't hold much energy, and the soundboard is good at throwing high frequencies into the room. Put those two together and τ drops to a couple of seconds, even on a 9-foot concert grand.