# Sound post (French, âme, "soul")

Source: https://arcosounds.com/glossary/soundpost

**The sound post is a small wooden dowel wedged inside a string instrument between the top and back, transmitting vibration and holding the body under string tension.**

It stands under the treble foot of the bridge, held in place by friction alone. Moving it by a fraction of a millimetre audibly changes the instrument's response and balance, which is why the French call it the soul of the instrument and why adjusting it is a luthier's job rather than an owner's.

If a sound post falls, which can happen if the strings are all removed at once, the instrument should be taken to a luthier and not played, since the top is no longer supported against the bridge's downward pressure. This is the practical reason string players change strings one at a time.

Canonical source: https://arcosounds.com/glossary/soundpost