The sustain pedal — which sustains nothing

I.The dampers

Resting on nearly every string of a piano is a damper: a small wooden block faced with felt. When you press a key, the action lifts that note's damper off its strings a moment before the hammer arrives; when you let the key go, the damper drops back and the string falls silent. That is the only reason a piano note ends when you release it. Left alone, the string would ring on for many seconds.

The right pedal lifts every damper at once and holds them all up. Nothing is added to the sound. Something is taken away — the silencing. That is why technicians, and careful teachers, call it by its accurate name: the damper pedal. Older English simply called it the loud pedal, and eighteenth-century Italian hides it in a word that seems to say the opposite: sordini, “mutes,” meaning the dampers themselves.

One detail gives the mechanism away. At the very top of the keyboard, roughly the highest octave and a half, there are no dampers at all. Those short treble strings die away so quickly on their own that nobody ever needed to stop them.

II.The effect the name leaves out

Lifting every damper frees more than the note you are playing. It frees all the other strings too. Strike a single C with the pedal down, and the strings of its octaves, its fifths and its other near relatives are now free to move. The overtones of the struck string travel through the bridge and soundboard, and those relatives begin to hum along in sympathetic resonance.

So a note played with the pedal down doesn't only last longer; it sounds larger, rounder, more like a room than a string. On an acoustic piano you can hear the difference before you even release the key. Pianists speak of the pedal opening the instrument, and a great deal of Romantic and Impressionist music is written for that open sound, not only for the length.

III.Reading Ped. and the star

The oldest marking is the abbreviation Ped. under the bass staff where the pedal goes down, and a star-like asterisk, ✱, where it comes up. Beethoven and Chopin marked their pedaling this way, and many editions still do. Modern scores more often draw a bracket line under the bass: it drops down where the pedal goes down, rises at the end, and shows a small notch, ^, wherever the pedal is changed in one quick motion. Very often nothing is marked at all, and the pedaling is left to the player. In most nineteenth-century music that means pedaling almost continuously and changing with every change of harmony.

The most famous pedal instruction in the repertoire is one sentence at the head of Beethoven's “Moonlight” Sonata, op. 27 no. 2: Si deve suonare tutto questo pezzo delicatissimamente e senza sordino — “this whole piece must be played very delicately and without dampers.” Without dampers means with the pedal. On Beethoven's lighter, quicker-fading piano, the harmonies were meant to blur into a haze. Pianists still argue about how literally to take it on a modern grand, whose sound lasts far longer.

The device is older than the pedal, too. On the Viennese pianos Mozart played, the dampers were raised by a knee lever under the keyboard, pushed upward while both hands kept playing. The foot pedal won out in the early nineteenth century.

IV.Why good pedaling comes late

The first instinct is to press the pedal with each new chord. It doesn't work: the dampers are still up from the last chord, the old harmony keeps ringing, and the two smear together. The technique that nearly every teacher ends up teaching goes the other way. Play the new chord, and in that same instant lift the pedal; then, while your fingers still hold the new notes, press it down again.

The pedal comes up with the chord and goes down just after it, always half a step behind the hands. It is called legato or syncopated pedaling, and it connects chords that the fingers alone could never connect, without letting them blur.

Between fully up and fully down lie finer shades. Half-pedaling lets the dampers just brush the strings, thinning the resonance without killing it. Flutter pedaling clears a blur gradually with a few rapid, shallow changes. Both belong to acoustic pianos and continuous pedals, where the foot can stop anywhere along the way.

V.On this piano

On Piano 1024 the sustain pedal is the space bar, in two modes: hold, momentary like a real pedal, and latch, where each tap toggles it. Release a key with the pedal down and the note is handed over to the pedal. Lift the pedal and every note it was carrying stops — except any key you are still holding down, which keeps ringing, just as it would on a real piano. The dampers here are equations, and they fall a little more slowly on the bass strings than in the treble, since heavy strings take longer to settle.

Two honest limits. A computer key is either down or up, so there is no half-pedal. And the synthesis does not model the sympathetic ringing of the freed strings: here the pedal keeps notes, but it doesn't open the room. (How the voices are built is on the sound page.)

The pedal also rescues a laptop problem. Many computer keyboards can report only about six keys at once. Latch the sustain and roll a big chord in note by note: every note keeps ringing. When you record, the pedal is written into the MIDI file as controller 64, which every music program reads as a sustain pedal.

The left pedal has its own note, and it is a stranger story.