The Soundpost by Otis Tomas

EVERY FIDDLE PLAYER knows that the soundpost, a small stick of spruce wedged between the top and back plates of a violin, plays an important role in the performance of the instrument. But simple as it is, the post's function is quite complex and little understood. About 1/4" in diameter, the soundpost stands upright just behind the treble foot of the bridge. Often called the 'soul' of the fiddle, its main purpose seems to be to harmonize the vibrations of the top and back. Structurally, a fiddle's arching alone can support the bridge, but played without the post, its tone is hollow and rough sounding; replacing the post puts the tone back into focus.

The post's resistance to the treble foot of the bridge also serves as a pivot by which the bridge's vibrations pump the bass bar. The relative position of the post to the bridge, ff-holes, and bar can be critical. Moving the post toward the bridge usually makes the tone tighter and more focused, whereas going back from the bridge makes it more open and hollow. Placing a shorter post further toward the edge can give more depth to the bass strings. A longer post nearer the centre can often, conversely, even out the tone of the strings.

These are only the most basic of generalizations. Other factors such as the tightness with which the post is put into place, the mass of the post itself, the relative tuning of the top and back plates, and the shape of the archings all have a bearing on how the post relates these variables.

It is impossible to give definite rules for proper soundpost adjustment, but there are a few rules of thumb that can be a good starting point:

1. The post should stand behind the bridge by a distance equal to the thickness of the top at that point.

2. It should be aligned with the treble foot of the bridge in the same way the bass bar is aligned under the left foot of the bridge.

3. It should stand vertically, its endgrain aligned perpendicularly to the grain of the top, ends fitting perfectly to the plates, and placed with only as much pressure as necessary to keep it from falling when the strings are off.

One should beware of tinkering unnecessarily with the post as every movement will require a period of readjustment to the new equilibrium which has been set up. Also, beware of damaging the ff-holes. Try always to work through the treble side to keep any accidental damage to one hole. Especially on historical instruments it is important to leave the left hole untouched, as evidence of the maker's artistry and intent.

 by Otis Tomas

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ast upddate 8/6/98