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Appendix B Synthesizer Basics 473
Tones, overtones, harmonics, and partials
The base, or core, frequency of a sound is known as its fundamental tone.
The waveforms of all sounds, apart from a basic sine wave, consist of the fundamental tone and
many other tones of dierent frequencies.
Nonfundamental tones that are whole-number multiples of the fundamental tone are known
as overtones or harmonics. (A tone with a frequency that is a fraction of the fundamental tone is
referred to as a subharmonic.)
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The fundamental tone is referred to as the rst harmonic. This is generally louder than the
other harmonics.
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A tone played at twice the frequency of the rst harmonic is called the second harmonic.
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A tone played at four times the frequency of the rst harmonic is called the fourth harmonic,
and so on.
Each of these harmonics has a timbral quality that is dierent from that of the fundamental tone.
In general, harmonics that can be multiplied or divided by a whole number, such as octaves,
odd-numbered or even-numbered harmonics, and so on, sound more “musical.”
Tones that cannot be multiplied or divided by a whole number are known as inharmonic
overtones, or partial tones. When you combine a number of these inharmonic overtones, it tends
to sound “noisy.”
Nonfundamental tones that are multiplied by fractional amounts—not whole numbers—are
called partials.
The frequency spectrum
A fundamental tone, when combined with various harmonics of dierent levels, is perceived
as a sound. The level relationships between these sonic elements change over time (controlled
by envelopes, as described in Amplier envelope overview). The combination of a number of
harmonics is referred to as the harmonic spectrum or, more commonly, the frequency spectrum.
The frequency spectrum shows all individual sonic elements in a sound. It is shown low to high,
and runs from left to right over time. The respective levels of all harmonics are reected vertically,
with taller spikes indicating higher levels.
Frequency spectrum
graphic of an organ sound
The illustration shows the level and frequency relationships between the fundamental tone
and the harmonics at a particular moment in time. These relationships constantly change over
time, which results in continuous changes to the frequency spectrum and, therefore, changes to
the sound.