circumflex is an excellent example of the bearing of wavelengths and
frequencies upon pitch.

Vibration of Diaphragms:--Sound waves in air have the power to move
other diaphragms than that of the ear. Sound waves constantly vibrate
such diaphragms as panes of windows and the walls of houses. The
recording diaphragm of a phonograph is a window pane bearing a stylus
adapted to engrave a groove in a record blank. In the cylinder form of
record, the groove varies in depth with the vibrations of the
diaphragm. In the disk type of phonograph, the groove varies sidewise
from its normal true spiral.

If the disk record be dusted with talcum powder, wiped, and examined
with a magnifying glass, the waving spiral line may be seen. Its
variations are the result of the blows struck upon the diaphragm by a
train of sound waves.

In reproducing a phonograph record, increasing the speed of the record
rotation causes the pitch to rise, because the blows upon the air are
increased in frequency and the wave-lengths shortened. A transitory
decrease in speed in recording will cause a transitory rise in pitch
when that record is reproduced at uniform speed.

_Timbre._ Character of sound denotes that difference of effect
produced upon the ear by sounds otherwise alike in pitch and loudness.
This characteristic is called timbre. It is extraordinarily useful in
human affairs, human voices being distinguished from each other by it,
and a great part of the joy of music lying in it.

A bell, a stretched string, a reed, or other sound-producing body,