his stretching process
has been reached, the cords relax slightly, and from this point on
each higher tone is made by _shortening_ the vibrating portion of the
cords; in other words, by decreasing the length of the glottis (the
aperture between the vocal cords). This point may become clearer if we
compare the process with tuning a violin string. The string may be a
third or a fourth below its normal pitch when the violinist begins to
tune his instrument, but by turning the peg and thus stretching the
string tighter and tighter, the tone is raised by small degrees until
the string gives forth the pitch that it is supposed to sound. But
this same string may now be made to play higher and higher pitches by
pressing it against the fingerboard, thus shortening the vibrating
portion more and more. The tuning process may be said to compare
roughly with the mechanism of the chest register of the human voice;
while the shortening of the string by pressing it against the
fingerboard is somewhat analogous to what takes place in the higher
registers of the voice.

We have now enumerated what seem to us to be the most essential
matters connected with vocal procedure; and if to such information as
is contained in the foregoing paragraphs the conductor adds the
knowledge that the _messa di voce_ (a beautiful vocal effect produced
by swelling a tone from soft to loud and then back again) is to be
produced by increase and decrease of breath pressure and not by a
greater or lesser amount of straining of the throat muscles; that
_portamento_ (gliding by infinitely small degrees in pitch from one
tone to another), although a valuable and entirely legitimate
expressional effect when used occasionally in a passage where its
employment is appropriate, may be over-used to such an extent as to
result in a slovenly, vulgar, and altogether objectionable style of
singing; and that whereas the _vibrato_ may imbue with virility and
warmth an otherwise cold, dead tone and if skilfully and judiciously
used may add greatly to the color and vitality of the singing, the
_tremolo_ is on the other hand a destroyer of pitch accuracy, a
despoiler of vocal idealism, and an abhorrence to the listener; if our
conductor knows these and other similar facts about singing, then he
will not run quite so great a risk of making himself ridiculous in the
eyes of the singers whom he is conducting as has sometimes been the
case when instrumentalists have assumed control