"Soft" Pedals

The left-side pedal, which enables a pianist to play with less volume, is often refered to as the “soft” pedal.  That name is used in a vertical piano, but in a grand piano, its proper name is the “una corda” pedal.  The pedals have different names because they operate differently.

In a vertical piano (and some grands), the soft pedal causes all the hammers to move closer to the strings.  Since the hammers are closer to the strings, they travel less distance before striking.  And because they travel less distance, they build up less momentum and, hence, less power.

Volume is a function of power:  the harder the hammer hits its string(s), the more sound will be produced.  In a vertical piano, then, the soft pedal enables you to play more softly by decreasing the force of the blow.

Pressing the soft pedal also changes the feel of the action by increasing the distance the key travels before you encounter resistance from the hammer mechanism.  This distance is known as “lost motion”, and increasing it can make the action feel sloppy.  But using the pedal can certainly make it simpler to play more softly.

(If you notice the keys moving when you depress the soft pedal, it means that the bridle straps are poorly adjusted.  Make a note to tell your technician about it so they can be set correctly during the next visit.)

A grand piano's “una corda” pedal works quite differently.  Rather than moving the hammers closer to the strings, the “una corda” moves the entire action sideways.

When the action is in its normal position, a hammer may hit one, two, or three strings, depending on where it is in the keyboard.  Bass strings are single; the next section higher has two strings per note (the bichords), and the rest of the piano has three strings per note (the trichords).

Shifting the action means that the hammer strikes either less of the string (in the bass) or fewer strings (in the bi- and trichords).  With the hammer striking fewer strings, less volume is produced.  The unstruck strings will vibrate sympathetically (see the Soundboard essay for more information), but they will not add much to the volume.

But when hammer alignment changes, tone changes, too.  Hammers develop string grooves (with slightly harder felt) as they are played.  When the action is shifted sideways by the una corda pedal, ungrooved and softer felt is exposed to the strings.  This softer felt produces a different, less bright tone which helps reinforce the sense of less volume.

If the una corda pedal shifts the action too far, a hammer may hit a string for the note above it.  And if it does not shift far enough, it will have little effect on the volume.  In either case, your piano technician should be able to adjust the mechanism so that it moves the correct distance.  As with all pedals, movement should be smooth and silent.

Many pianists ignore the “soft” pedal and its creative potential.  Give yours a try and see what difference it can make in your playing.  And talk with your technician if you have questions or notice problems.