Piano pedals (1) - the sustain pedal

 

As a couple of people have asked me recently, I thought it might be useful to run through a brief history of how the pedals on a piano evolved and the mechanics of how they work. This is the first in a planned series of three articles.

Two pedals or three?

The first question is - how many pedals does the typical piano have? The answer may depend on which part of the world you live in. In Europe, the great majority of older pianos will have only two pedals - only since around the 1970s and 80s has the middle pedal become commonplace on new models. On the other hand, in North America, I understand that three pedals is generally the norm, and the situation may vary in other parts of the world. In any case, almost any piano will have either two or three - a few historic instruments (typically from the 1860s or earlier) may have only one pedal (normally the sustain pedal); also in a very few cases there may be four or more (of which more in a later article).

The exact functions of pedals on an upright piano is typically different from a grand piano, and some uprights differ from each other, so to ease into the discussion I'll deal with the one pedal which does more or less the same thing on every piano, and is almost always located in the same place - it's the right-hand or sustain pedal.

The sustain pedal (right-hand pedal) - also called the damper pedal

When pianists talk about "using the pedal", it is the right-hand or sustain(-ing) pedal they normally mean. This has a similar function on more or less every instrument, which is to lift off all the felt dampers that prevent the strings from ringing on after being struck by the hammer. Because of this, the pedal is sometimes referred to as the damper pedal or the loud pedal, though the latter term is often held to be incorrect since it does not make the notes any louder; nor is it the pedal's particular purpose (it is often used in quiet passages). However, its use does change the timbre of a note when struck, as it allows the strings of the other notes to vibrate sympathetically. On some early pianos, the sustain pedal is the only pedal though it was not the first to be invented (that was the una corda, of which more in the second article).

The first maker known to have used the sustain pedal mechanism in essentially its current form was Johann Andreas Stein (1728-92), although his pianos featured knee pedals rather than the modern foot-operated ones. This was a development of an earlier idea by Gottfried Silbermann (1683-1753), but this earlier device was a hand stop, so could only be switched on and off whilst the piano was not being played. A picture of a Stein grand piano, with the knee pedal visible, can be seen on the Cobbe Collection website here:
http://www.cobbecollection.co.uk/collection/15-grand-piano/

John Broadwood in 1783 used the modern concept of the sustain mechanism operated by a foot pedal on his grand pianos, though this may have been used on some earlier English-made instruments.

How the sustain pedal works

Although this pedal has the same basic function on every piano, it actually works in a slightly different way depending upon the type of piano you have. 

Underdamper uprights (all modern and some older uprights)

All modern upright pianos and some older instruments have dampers that are located underneath and behind the hammers - this is called an "underdamper action". This picture shows the bass section of a Yamaha U1 - I have pressed the pedal down and as you can see, the dampers have come away from the strings (the position of the dampers is shown by the red arrows).

When the pedal is pressed, it moves a pivoted rod (usually wooden on older pianos, sometimes metal on newer ones) called a rocker, and this pushes up the pedal stick, normally at the left-hand side of the case.

This picture shows a typical arrangement of two pedals, the pedal rockers and pedal sticks on an older German-made upright piano. When the pedal is pressed down, the pedal bolts pull down the pedal rocker at the right-hand side - the left-hand side pivots up raising the pedal sticks (at the left side of the case).The rocker is returned to position by a spring.

The pedal stick engages with a hinged metal rod at the back of the dampers, called the damper lift rod, which pushes the tails of the dampers forwards and brings the heads away from the string.

This picture shows a modern Yamaha U1 action from the back, removed from the piano so you can see what is happening. The pedal stick comes up where my hand is and the rod (the end of which can be seen under the green arrow) moves the damper tail outwards, moving the head back from the string.

You will also note that the top notes (typically the top couple of octaves) on any piano will not have dampers, as they sustain for such a short while that damping is unnecessary.

The invention of underdampers goes back to 1829 when they were featured in an action design by the French piano makers Blanchet et Roller.

Overdamper uprights (some older pianos)

An 1890s German overstrung upright with overdampers

If your upright piano looks a bit like this with the top door removed, you have an overdamper model. Overdampers are very common in many European-made pianos from before the Second World War, but the design gradually disappeared over time and ceased to be made at all after about 1950 (outside Europe I believe they may be much less frequently-encountered). They can very easily be identified by the long wires at the front of the action which operate the dampers, located on a separate damper rail above the line of the hammers. Unlike the underdamper action, which relies on springs to push the dampers back on to the strings, the overdamper mechanism is gravitationally operated (there are often weights located in the wooden damper bodies). Please note however that some older pianos - including pre-1900 models - have the modern-style (underdamper) mechanism.

On these pianos, the dampers are normally lifted by a wooden or metal rail underneath the damper bodies - the blue arrow on the diagram shows the end of the damper lift rail and the top of the pedal stick (which is pushed up by the pedal). The damper body (the piece of wood connected to the top of the long wire) links to a right-angled wire that connects to the damper head.

There is some variation in these arrangements - a few (normally older) overdamper models have a spring-loaded damper rail which is pulled away from the strings, or a hinged rail which moves upwards with the pedal, drawing back the dampers in both cases.

Overdampers are similar to a design used by Robert Wornum in his patent for a "double action" in 1826, which is the basis for all modern upright actions. It appears that most English manufacturers used this design through the mid-nineteenth century, whereas some French makers used underdampers; quite a lot of German makers followed the English practice. From the latter part of the nineteenth century onwards until around 1950, overdampers were gradually phased out as more and more manufacturers switched over their action designs. However some noted makers (such as the German firm Blüthner) continued to use overdampers until relatively late on.

Grand pianos

On a grand piano, the dampers sit on top of the strings (except for a few older models that have them underneath) and are easily visible when the lid is raised. Each damper is connected to a wire, which goes through a hole in a piece of wood through the damper guide rail, and connects though a pivoting knuckle to the damper underlever, which is attached to a rail underneath the soundboard. Note that under normal circumstances these underlevers are difficult to see with the action inside the piano.

This arrangement is shown in the diagram below:

When the key is pressed down (the front of the key is off the right-hand end of this diagram), it pivots on the balance pin (coloured blue) and the back of the key is pushed upwards (red arrow). This will propel the hammer up toward the string, but the part we're interested in here is that the very back of the key (shown in red) will rise up and push up the damper underlever, so lifting the damper head (green) and felts from the string.

If the pedal is pressed, this typically connects to a metal strip that pushes up a dowel underneath the damper lift rail (shown in orange) - this raises all the damper underlevers and the dampers (green), regardless of whether the key is pressed down or not.

You will also note that in the grand action, the damper mechanism is effectively separate from the main action, which will be important in the next article!

When the sustain pedal isn't working

The pedal is extremely important for expression in many piano pieces - especially those from the romantic era - so pianist Eliane Rodrigues had to think on her feet when things went wrong during a performance in Rotterdam. Here's what happened when the piano had to be taken off-stage, using a descending trapdoor, and replaced:

The other pedals (left pedal and middle pedal, where there is one) will be covered in two further articles.