e human voice, perfect as it may be in tone, is yet always very
deficient in compass, as is obvious from the fact that the bass voice,
the barytone, the contralto, and the soprano have all different
registers, and are all required to produce a complete vocal harmony. If
we could make organ-pipes with movable, self-regulating lips, with
self-shortening and self-lengthening tubes, so that each tube should
command the two or three octaves of the human voice, a very limited
number of them would be required. But as each tube has but a single
note, we understand why we have those immense clusters of hollow
columns. As we wish to produce different effects, sometimes using the
pure flute-sounds, at other times preferring the nasal thrill of the
reed-instruments, we see why some of the tubes have simple mouths and
others are furnished with vibratory tongues. And, lastly, we can easily
understand that the great interior spaces of the organ must of
themselves furnish those resonant surfaces which we saw provided for, on
a small scale, in the nasal passages,--the sounding-board of the human
larynx.

* * * * *

The great organ of the Music Hall is a choir of nearly six thousand
vocal throats. Its largest windpipes are thirty-two feet in length, and
a man can crawl through them. Its finest tubes are too small for a
baby's whistle. Eighty-nine _stops_ produce the various changes and
combinations of which its immense orchestra is capable, from the purest
solo of a singing nun to the loudest chorus in which all its groups of
voices have their part in the full flow of its harmonies. Like all
instruments of its class, it contains several distinct systems of pipes,
commonly spoken of as separate organs, and capable of being played alone
or in connection with each other. Four _manuals_, or hand key-boards,
and two _pedals_, or foot key-boards, command these several
systems,--the _solo_ organ, the _choir_ organ, the _swell_ organ, and
the _great_ organ, and the _piano_ and _forte_ pedal-organ. Twelve pairs
of bellows, which it is intended to move by water-power, derived from
the Cochituate reservoirs, furnish the breath which pours itself forth
in music. Those beautiful effects, for which the organ is incomparable,
the _crescendo_ and _diminuendo_,--the gradual rise of the sound from
the lowest murmur to the loudest blast, and the dying fall by which it
steals gently back into silence,--the _dissolving views_,