Just like in a car the right pedal makes the piano go faster and the left one stops it. Wait … that can’t be right.
Let’s back up. Typically a piano will have three pedals although on some, especially older, models you might only see two and there have even been instruments with four or five pedals. We need to distinguish not only between the left, center and right pedals but between pedals on an upright piano compared to a grand piano.
The right pedal on a piano, grand or vertical, is universally a Sustain pedal. What it does is lift the dampers off the strings so that the sound sustains, that is the strings continue to produce sound until they naturally quit vibrating. When you lift your foot off the pedal the dampers return to their normal resting position on the strings, “dampening” or stopping the strings’ vibration and thereby the sound. Due to the difference in orientation of the action, dampers move out horizontally from the strings on a vertical piano while on a grand they lift up above the strings.
We can generally consider the left pedal on a piano to be the Soft pedal, although its function will vary somewhat depending on whether the piano is a grand or vertical and other considerations. On most grands the normal function of the left pedal is to shift the entire action slightly, generally to the right. What this does is cause the hammer to strike one fewer string than normal for that note. (This is one example of why proper alignment and regulation of the action, stringing and other design aspects of the instrument are so important.)
The term used to describe this function is una corda, Italian for “one string”, somewhat a misnomer but derived from Cristofori’s original invention. While this does reduce the volume of sound, hence “soft pedal”, it actually has a more complex effect. The quality of the sound produced is changed since a different portion of the hammer surface is hitting the strings. Again, a number of aspects come into play here such as the condition and voicing of the hammer, alignment and seating of the strings, etc.
Unless it is a rare instrument with the function, most vertical pianos do not have any means for shifting the action such as we find on grands. Therefore the left pedal is designed to move the damper rest rail closer to the strings, thereby reducing the distance and force of the hammers against the strings.
What the center pedal of a piano does is the least predictable of the three. On a grand it is often a Sostenuto pedal, which is a single note sustain. This feature is not prevalent in most written music but when it is called for there is no real substitute for a genuine Sostenuto. The mechanism controlled by the pedal allows the pianist to apply sustain to only selected keys while the others play normally with no sustain.
On some grands the middle pedal is a bass damper lift (only the bass dampers are lifted off the strings rather than all dampers) instead of a sostenuto.
The middle pedal on an upright piano may on rare occasions be a sostenuto (usually found only on high end quality instruments) but more often is:
• a second soft pedal
• a practice pedal which is basically a soft pedal you can lock into position
• a practice pedal which lowers a felt strip between the hammers and strings
• a dummy pedal which gives the piano a third pedal but actually does nothing
Sometimes the center pedal or fourth or fifth pedals offer unique sounds such as a mandolin or harpsichord or chimes. The Crown piano by Geo. P. Bent and the Wing and Sons were two manufacturers which offered such extra pedal features in the late nineteenth century. The “rinky-tink” effect has been a little more common on player pianos, although that is often accomplished with a hand lever rather than foot pedal.