This introduction is meant to a guide to those who have little or no knowledge of violin construction, particularly
concerning the sound post. Hence it will be largely explained in simple, practical terms. Below is a diagram of
a violin cut laterally throught the center that illustrates the position of the sound post in a completed violin.
The sound post is a small dowel of Spruce that is held by friction between the top and back plates of a violin
(viola, cello, or string bass), situated under the treble side of the bridge. It has both structural and tonal
Structurally, it supports the top plate, acting like a pillar under the bridge. Without it, a violin would "cave
in" on the treble side. A good violin, however, may not be harmed if it is without a sound post for a short
period of time, but an instrument should not be left in this situation for long.
Acoustically, the sound post transfers vibrations from the top plate to the back plate of the instrument. It
also alters the vibration of the top plate. Its placement, length, thickness, grain orientation, and wood selection
influence the tone of an instrument. An instrument without a sound post will sound weak, thin and hollow.
On the bass side of an instrument is a "bass bar", a cross section of which can be seen in the illustration
above. It has both acoustic and structural roles as well.
View of a sound post through the end pin hole at the bottom of the violin. Also seen are some of the cleats which
reinforce the back seam.
The sound post can easily be seen through the f-hole on the treble side of the instrument.