Artificial Harmonics.
The name "artificial" is used merely in contrast to "natural," they are only artificial in the sense that they are produced on an artificial or "made" basis, instead of being in the key of the open string.
If one was restricted to the use of natural harmonics it would be impossible to play scale passages, or any passages foreign to the key of the four open strings. However by causing the string to be shortened by the employment of a stopped note the pitch of the fundamental note may be raised to any desired height, the harmonics being produced exactly as before, on the fresh root thus formed; the harmonic being in the key of the shortened string. In playing artificial harmonics on the violoncello it is usual to employ the thumb for the stopped note, the third finger should then be caused to touch the string lightly at one of its nodal points, the distances of course being now calculated from the thumb to the bridge. Owing to the sometimes great length of string between the stopped note and the bridge it is often found impossible to use any but the smaller divisions, the form most often met with being harmonics produced by fourths, that is, the third finger touching the string at the interval of one fourth (stopped note) above the thumb: the harmonic thus produced will be two octaves above the pitch of the note stopped by the thumb. Whole passages are written for this form of artificial harmonics. To the student who has thoroughly mastered octave passages in stopped notes the technical difficulties presented ought to be easily conquered, as the same technique really suffices for both; the only difference being that whilst octaves are played across two strings—artificial harmonics by fourths are played with the same fingering and the same intervals on one string.
With respect to the bowing of harmonics, the peculiar manner in which the string vibrates during the production of harmonic notes must be taken into consideration. It is important to notice that the vibration of the string near the nodal points is the least intense (see double lines in diagram), whereas the part mid-way between the nodes vibrates with the greatest intensity; if the bow is caused to pass near one of these nodes it may possibly give a greater vibration to that portion of the string than is required, which would have the effect of displacing the natural division, and placing of the nodes, thus causing confusion or perhaps another harmonic than the one intended to be produced. It is general to give an all round rule that in playing harmonics the bow must always be drawn close to the bridge, the student will comprehend that the smaller the division of the string used to produce the harmonic, the greater need will there be to attend to this rule. The progression of harmonic notes should be clearly defined; in passages composed wholly of harmonics it may sometimes be found advisable to use a down bow-stroke for each note, slightly striking the commencement of each harmonic; this will give the necessary attack, and will cause each note to ring out clear as a bell, providing the fingering is correctly managed.
Harmonics are indicated in various ways, sometimes causing much confusion and indecision as to what is really required; thus in a single composition it is possible to find the real notes which are to be produced being given with the word "harmonique" or "flageolet" or sometimes the sign O (usually employed for natural harmonics) added, the player to produce the harmonics as he pleases; again the position of the node which produces the harmonic will be indicated by a blank note, the pitch of the harmonic to be produced being left to fate and the performer. To indicate artificial harmonics it is usual to write the stopped notes as an ordinary passage, then with the aid of blank notes the positions where the string has to be lightly touched are shown.
[CHAPTER XIV.]
Special Effects—"Trick Staccato"—Various Methods of Producing Chromatic Scale Passages—"Sul Ponticello" Bowing and "Bowed" Harmonics—Flautando—Pizzicato Glide and Grace Notes!