On the piano every note is ready and waiting for us to touch. Not so on the violin. Every note (except the open ones) the performer has to make. He has only four fingers to make these notes because his thumb simply helps the hand take its various _positions_. Generally speaking, there are seven positions; for the three still higher ones are rarely used. With each position, the hand is shifted a little higher on the neck of the violin; and the thumb and wrist gradually turn, the thumb from and the wrist towards the face of the player. As the hand creeps up upon the instrument, the fingers come closer together and the notes lie nearer to one another on the strings. The flexible little finger can be extended still further in each position while the position of the wrist and thumb is still retained. As each finger presses the string tightly and firmly, the player shortens the vibration (or length) of the string and gets a special note. He learns to know his fingerboard and where all the notes lie on the strings with their intervals of whole tones and half-tones; and just what finger to place on these notes if he wants to play in the first, third, or fifth, position,—and so forth. The violinist rarely plays in any one position; but lets his wrist move up and down and his fingers fly all over the fingerboard, playing in all the positions just as he pleases. The player has to have a very accurate knowledge of the fingerboard; and then, beyond that knowledge, a very correct ear so that he may play in perfect tune, or good _intonation_, as it is called. A beginner on the violin finds this task even harder than to learn to draw a firm, straight, even and liquid bow. He has to listen to every note he produces and test it, as it were, until, after a time, he learns the fingerboard and his fingers drop on the right spots automatically. Of all musicians the players of strings have the most sensitive, accurate and the best trained ears. [Illustration: VIOLIN _By Guarneri del Gesù. Owned by Paganini_] On the strings certain other notes are produced called harmonics. At certain places on a string there are nodes, as they are called, where, by lightly touching the string with the finger, over-tones are set vibrating. These are very strange and curious. They sound ethereal and flute-like. There are two kinds of harmonics: natural harmonics and artificial harmonics. The natural harmonics are found on the open strings at certain definite places. There are _five_ of these on each string. The artificial harmonics are produced by stopping the string with one finger and touching it lightly with another. These harmonics are harder to master; and they are a great worry to a violinist, because if his violin gets out of tune (drops a little from the heat of a concert hall, perhaps) the proper harmonics cannot be played. The question of harmonics is one that belongs to the science of acoustics and it is a very hard one to understand.