almost down to our own time, were restricted in the use of them
because they were merely natural tubes, and their notes were limited
to the notes which inflexible tubes can produce. Within this century,
however, they have all been transformed from imperfect diatonic
instruments to perfect chromatic instruments; that is to say, every
brass instrument which is in use now can give out all the semitones
within its compass. This has been accomplished through the agency of
valves, by means of which differing lengths of the sonorous tube are
brought within the command of the players. In the case of the
trombones an exceedingly venerable means of accomplishing the same end
is applied. The tube is in part made double, one part sliding over the
other. By moving his arm, the player lengthens or shortens the tube,
and thus changing the key of the instrument, acquires all the tones
which can be obtained from so many tubes of different lengths. The
mouth-pieces of the trumpet, trombone, and tuba are cup-shaped, and
larger than the mouth-piece of the horn, which is little else than a
flare of the slender tube, sufficiently wide to receive enough of the
player's lips to form the embouchure, or human reed, as it might here
be named.

[Sidenote: _The French horn._]

[Sidenote: _Manipulation of the French horn._]

The French horn (Plate IX.), as it is called in the orchestra, is the
sweetest and mellowest of all the wind instruments. In Beethoven's
time it was but little else than the old hunting-horn, which, for the
convenience of the mounted hunter, was arranged in spiral
convolutions that it might be slipped over the head and carried
resting on one shoulder and under the opposite arm. The Germans still