And now let us consider carefully the three important and highly mysterious organs of the violin. Yes, I am calling them organs. Perhaps I had even better say organs and nerves. These are the bridge, the sound-post and the bass-bar. The two latter are invisible. The bridge, a delicately cut little arch of maple, or sycamore, higher on one side than on the other, perforated curiously but according to a form learned through the experiments of centuries, has been called the “_tongue of the violin_.” The treble foot of the bridge stands firm and rigid on that part of the belly made rigid by the sound-post. The bass foot of the bridge rests on that part of the body, or belly, which vibrates freely, these vibrations being increased and regulated by the bass-bar. Through this bass foot of the bridge the vibration of the strings is communicated to the belly and thence to the mass of air in the violin. The treble foot of the bridge is _the centre of vibration_. The action of the bridge, however, really depends upon the sound-post. [Illustration: A LITTLE SAVOYARD IN PARIS WITH VIELLE, OR HURDY-GURDY] The sound-post has been called “the _soul of the violin_.” It is a little pine stick, a few inches long, about the size of a large cedar pencil. It is placed upright about an eighth of an inch to the back of the right foot of the bridge. “Through it pass all the heart throbs, or vibrations, generated between the back and the belly. There the short waves and the long waves meet and mingle. It is the material throbbing centre of that pulsating air-column defined by the walls of the violin, but propagating those mystic sound-waves that ripple forth in sweetness upon ten thousand ears.”[2] The bass-bar (or sound-bar) has been called “_the nervous system of the violin_.” It is an oblong piece of wood glued lengthwise to the belly. It runs in the same direction as the strings and acts as a beam, or girder, to strengthen the belly against the pressure of the left foot of the bridge. The bass-bar has to be cut and adjusted to meet the requirements of every violin; and only long experience can determine how _long_, how _thick_ and exactly _where_ the bass-bar should be made and placed. The fraction of a line makes all the difference in the world. The bass-bar is the only member, or organ, of the violin’s body that has undergone any change since the days of Antonio Stradivari. Owing to the increased pitch (higher tuning) of the present time, the tension, or pull, of the strings equals _eighty_ pounds! Think of it—this frail-looking, delicate, little violin stands a strain of eighty pounds! In Stradivari’s time this tension was sixty-three pounds. So in modern times it has been found necessary to strengthen the bass-bar by giving it extra depth in the centre and adding to its length.