Bouts, Bridge, and Soundpost
The side and back of the violin body are usually made of maple. The sides are known as bouts, and are divided into three sections, the upper bout or shoulder, the middle or C bout, and the lower bout.
The bridge is made of seasoned maple and is not glued or attached to the top. It is held in place by tension on the strings. For this reason, strings should always be changed one string at a time.
Over time, the bridge may move or bend slightly due to changing tension on the strings. Periodic bridge adjustments are a part of basic care and maintenance.
Attached to the inside of the top is the bass bar.The bass bar is glued to the top, and does not require maintenance. Inside the instrument, just behind the right foot of the bridge, is the soundpost. When the instrument is played, the soundpost and bass bar help to transmit vibrations from the top of the instrument throughout the entire body of the instrument, allowing greater projection of the tone.
The soundpost is not glued. It is held in place by the tension on the strings. If the bridge collapses, the soundpost may fall. Soundposts may move slightly as the top of the instrument expands and contracts. The position of the soundpost has a huge effect on the tone and response of the instrument. For that reason, it is a good idea to have the soundpost reset periodically, especially if you notice a big change in the sound of your instrument.