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Lesson 50: Pitch & Frequency
This lesson explains what musical pitch "actually is", i.e.
what happens in the physical world to make a pitch, and how we
measure pitch.
First, a brief definition of sound: Sound is what happens
when an object vibrates or "shakes"; the shaking object makes the
air shake; and the shaking air makes your ear shake. Note that
these "sound shakes" are too weak, and too fast, for your body to
feel them, which is why we have ears that can feel them, as
sound.
However, not all sounds have pitch. When the air shakes back and
forth ("vibrates"), over and over, at a constant speed, long enough
for your ear to "measure" the speed, that's when you hear a
pitch. Slow vibrations make "low" pitches; fast
vibrations make "high" pitches.
A pitch is measured by its frequency, which just means its "speed" in
vibrations per second. Vibrations-per-second is also called
Hertz; the abbreviation for Hertz is Hz. For example,
the pitch "A above middle C" has a frequency of 440 Hz; that
means that it's vibrating back and forth 440 times in a second.
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