The halo of sound which streams from the beginning and end of the “Lohengrin” prelude is produced by this device.  High and close harmonies from divided violins always sound ethereal.  Besides their native tone quality (that resulting from a string stretched over a sounding shell set to vibrating by friction), the violins have a number of modified qualities resulting from changes in manipulation.  Sometimes the strings are plucked (pizzicato), when the result is a short tone something like that of a banjo with the metallic clang omitted; very dainty effects can thus be produced, and though it always seems like a degradation of the instrument so pre-eminently suited to a broad singing style, no less significant a symphonist than Tschaikowsky has written a Scherzo in which the violins are played pizzicato throughout the movement.  Ballet composers frequently resort to the piquant effect, but in the larger and more serious forms of composition, the device is sparingly used.  Differences in quality and expressiveness of tone are also produced by varied methods of applying the bow to the strings:  with stronger or lighter pressure; near the bridge, which renders the tone hard and brilliant, and over the end of the finger-board, which softens it; in a continuous manner (legato), or detached (staccato).  Weird effects in dramatic music are sometimes produced by striking the strings with the wood of the bow, Wagner resorting to this means to delineate the wicked glee of his dwarf Mime, and Meyerbeer to heighten the uncanniness of Nelusko’s wild song in the third act of “L’Africaine.”  Another class of effects results from the manner in which the strings are “stopped” by the fingers of the left hand.  When they are not pressed firmly against the finger-board but touched lightly at certain places called nodes by the acousticians, so that the segments below the finger are permitted to vibrate along with the upper portion, those peculiar tones of a flute-like quality called harmonics or flageolet tones are produced.  These are oftener heard in dramatic music than in symphonies; but Berlioz, desiring to put Shakespeare’s description of Queen Mab,

    “Her wagon-spokes made of long spinner’s legs;
    The cover, of the wings of grasshoppers;
    The traces, of the smallest spider’s web;
    The collars, of the moonshine’s watery beams—­”

into music in his dramatic symphony, “Romeo and Juliet,” achieved a marvellously filmy effect by dividing his violins, and permitting some of them to play harmonics.  Yet so little was his ingenious purpose suspected when he first brought the symphony forward in Paris, that one of the critics spoke contemptuously of this effect as sounding “like an ill-greased syringe.”  A quivering motion imparted to the fingers of the left hand in stopping the strings produces a tremulousness of tone akin to the vibrato of a singer; and, like the vocal vibrato, when not carried to excess, this effect is a potent expression of sentimental feeling.  But it is much abused by solo players.  Another modification of tone is caused by placing a tiny instrument called a sordino, or mute, upon the bridge.  This clamps the bridge, makes it heavier, and checks the vibrations, so that the tone is muted or muffled, and at times sounds mysterious.