In string instrument, the sound post is a cylinder device inside the instrument under the treble end of the bridge, spanning the space between the top and back plates and held in place by pressure. It serves as a structural support for an archtop instrument, transfers sound from the top plate to the back plate and alters the tone of the instrument by changing the vibrational modes of the plates. On violins, the dowel is small. On a double bass, a thick, string dowel is used.
The sound post is sometimes referred to as the âme, a French word meaning "soul". The bow has also been referred to as the soul of these instruments. The Italians use the same term, anima, to describe sound post.