TOUCH

Touch refers to the player’s control of a piano key when the key is depressed with a certain intensity causing a hammer to strike the string(s) with a correlating intensity and velocity allowing the player to express emotion through music.

Along with tone, discerning pianist will choose a piano for purchase or performance based on touch. Pianos of the same make and model inherently have similar touch characteristics. Like tone, certain differences can and do exist. Touch can be characterized as heavy, light, or somewhere in between. Key to hammer response has developed to a standard ratio.

The action is the mechanical aspect of the piano that facilitates the touch to tone relationship. The action is the “heart of the piano.” A piano action has over 9000 parts that require periodic adjustment to critical tolerances that allow a player to control the dynamics of the music played. “Necessity is the mother of Invention.” The modern piano action evolved over several centuries to the point where a player can control the dynamics of play, expressing emotion, through touch. There has not been much change in action design in about 120 years.

Grand Action (Courtesy of MSN Encarta)

The following description of what occurs when you depress a grand piano key was taken from PIANO SERVICING TUNING & REBUILDING, (Second Edition) by Arthur A. Reblitz

“Every time you depress a key a whole chain of events occurs.  On a grand piano, when you depress a key slowly, the capstan pushes on the wippen, which pushes on the jack, which pushes on the hammer knuckle and begins lifting the hammer, when the hammer is halfway to the strings the back end of the key begins to raise the damper from the strings.  As the key continues down, and the hammer is almost to the strings, the jack tow bumps into the letoff button, and the jack slips out from under the knuckle.  The hammer continues by inertia, hits the strings and rebounds.  By the time the hammer rebounds, the jack is already tripped out from under the knuckle, so the knuckle lands on the repetition lever instead.  The downward force of the hammer during medium or loud playing is stronger than the repetition lever spring, so the hammer knuckle pushes the repletion lever down, pivoting it on its flange.  The downward motion continues until the hammer tail catches on the back check, and the hammer remains in this checked position as long as you hold down the key.’ 

‘When you release the key in slow motion, the backcheck releases the hammer tail, allowing the repetition lever to push the hammer upward until the repetition lever comes to a stop on the drop screw.  As the back end of the key continues to go down, the wippen follows, and as the jack drops, it pivots back under the knuckle when the jack toe clears the letoff button.  Because the jack clears the letoff button when the front end of the key is less than halfway up, the action ready for another complete cycle without the key needing to return o its rest position.  When the key is fully released, it lowers the damper to the strings, muting the sound.  This sequence occurs much faster than the eye can follow, and in far less time than it takes to describe it in writing.”

I could not have said it better myself.

The action of a vertical piano is similar. However, a vertical does not have a repetition lever. On a vertical, a depressed key must return all the way back to its original position before it can be depressed again, which will cause the hammer to strike the key.

The invention that revolutionized piano playing was the “escapement” mechanism, found on both the grand and the vertical pianos. The escapement allows the hammer to strike the string and fall back a short distance so the note can be played again quickly. You can play a note on a grand piano more rapidly when playing softly due to the repetition lever.

REGULATION

As mentioned, the piano action has over 9000 parts that interact when you depress a key and the hammer hits the strings. These parts have to be in adjustment or regulation for the hammer to respond correctly when the key is depressed. These parts, made of wood, felt, buckskin, and metal are affected by wear, settling, and humidity fluctuations. Tolerances of thousandths of an inch are required.

A new piano of good quality is regulated to specifications by the manufacturer. Shipping the piano could put the action out of regulation. A reputable retailer will regulate the piano prior to display or delivery. Once the new piano is in the home, a tuner-technician might have to perform some minor adjustments or regulations to meet proper touch specifications. After that, the need for regulation is determined by the quality of the instrument, the amount of play, and temperature and humidity fluctuations. If you are a practiced pianist, you will know when your piano requires regulation.

You do not have to be a practiced pianist to detect certain out of regulation issues. Some of the affects of an out of regulation action include:

Hammer double striking the string

Hammer blocking the string, not allowing the string to resonate

Unable to play the note a second time in secession

The key not returning to its rest position after depressing it

“Sluggish” key

Unable to play “forte” (loudly-forcefully)

Unable to play “pianissimo” (very softly)

Sometimes only one or a few notes are out of regulation. This is usually due to a humidity issue that affects a certain key action mechanism that is susceptible to moisture flexibility. (The flange bushing might have a thousandth of inch too much felt and has swollen around the flange pin.) These types of issues are usually corrected at the time of a tuning.

WHY REGULATE?

An out of regulation piano does not allow a player to play the piano the way it was meant to be played and heard. There is nothing more frustrating to a player to depress a key and the response expected and required does not happen. This can frustrate the student player and possibly inhibit improvement and stifle interest. An accomplished pianist will not tolerate an out of regulation piano.

DAMPERS AND PEDALS

Two other mechanical aspects of the piano require periodical regulation. These are the damper assembly and the pedal trap-work. The action, damper assembly, and pedal trap work are interrelated.

The purpose of the damper is to mute or silence the strings. Each note, except for the upper treble notes, has a damper that is individually activated by the depression of a key. (The upper treble strings do not have dampers due to their short length, which results in shortened resonance. In addition, the upper treble strings, when tuned, add vibrancy to the piano. Being un-dampened, they resonate in harmony with strings that are played in other sections of the piano.) When a key is depressed, the corresponding damper must begin moving off the string when the hammer travels half the distance from its rest position to the string. This allows the string to resonate when the hammer hits the string. The damper must fall back on the string and mute the strings resonance, when the pedals are not engaged, when the key is released.

Most pianos have three pedals. The right pedal is always the sustain pedal. The middle pedal and left pedal have different functions depending on the make, quality, and style of piano (grand or vertical).

When the sustain pedal is depressed, all of the dampers are lifted off their strings allowing all the stings that are played to resonate or sustain. (Certain other strings will also resonate in harmony with the string(s) being played.)

The middle pedal in quality grand pianos and some verticals is known as the “sostenuto” pedal. When one or more notes are played and the sostenuto pedal is depressed, these notes will sustain after the key is released, allowing the pianist to play other notes that will not continue to sustain after the key is released.

In other pianos, the middle pedal will sustain just the bass notes. In some verticals the middle pedal will engage a mechanism that has a “mute felt” attached, lowering it between the hammers and the stings so the hammers hit the felt prior to the strings, muting the sound. In the past (and they are still available today), this mechanism lowered a strip with metal tabs, causing the hammers to hit the metal tabs prior to the strings, creating a “honky-tonk” sound.

The left pedal of most grand pianos is knows as the “una corda” pedal. This pedal shifts the key bed and action to the right slightly, causing the hammers that normally hit three-string unisons to only hit two strings. This changes the volume and tone, but not the touch. The tone is affected due to different surfaces of the hammers hitting the strings

In vertical pianos, the left pedal usually engages a mechanism that pushes the hammer rest rail and hammers closer to the strings by half the distance. This inhibits forceful play and reduces the volume. This affects the touch. Most teachers discourage the use of this pedal

Like the action, the dampers and pedals are affected by quality, play, and humidity fluctuations. Your tuner-technician can make necessary adjustments at the time of tuning. Some of the affects of dampers and pedals being out of regulation include:

Notes sustaining after release of the key (Dampers sticking in raised position)

Dampers not resting on strings properly causing some resonance to bleed through

Squeaking pedals

Too much play in pedals

Hammers hitting neighboring strings causing two notes to play (una corda issues)

Your tuner-technician can advise you if more in-depth regulation is required.