Piano Bridges

When you play the piano, what you hear is produced mainly by the soundboard, the very thin sheet of wood under or behind the strings.

Sound is vibration traveling through air.  And piano strings vibrate when struck by a hammer.  But even the biggest string can’t move enough air to be heard very far away.

Using a soundboard to move the air solves that problem in pianos and all other acoustic, stringed instruments.

But how does the vibration get from the strings to the soundboard?  Bridges!

A bridge is a piece of wood that sits on the soundboard and transfers vibrations from the string to the soundboard.  A piano has two bridges on the soundboard:  a bass bridge and a treble bridge.  (A guitar, in contrast, has one bridge on it body, near the point where the strings end.)

In most stringed instruments, the strings are held against the bridge by pressure.  A piano, however, also uses tilted “bridge pins” to hold the strings firmly against the bridge so that all the vibration passes cleanly across to the soundboard.

The strings weave between the pins, which puts a great deal of pressure on the pins.  And the strings’ vibrations add to that pressure, especially in the bass, where the strings are so heavy and stiff.

Since the cells in dry wood shrink and can't withstand as much pressure, when a piano's environment is dry.  And if the pins move, the bridge can crack.

A cracked bridge can cause trouble in several ways:

  • poor tone from the loss of vibration transmitted to the soundboard
  • unwanted vibrations from the loosened pins
  • tuning instability from strings which are not secured properly
Ask your piano technician for more information about the condition of your piano’s bridges and how to keep them in good shape.  And if your piano is in a dry or changeable environment, ask for information about how to stabilize it.  You’ll be glad you did!