10.6

702Logic Pro Instruments
• A tone played at twice the frequency of the first harmonic is called the second
harmonic.
• A tone played at four times the frequency of the first harmonic is called the fourth
harmonic, and so on.
Each of these harmonics has a timbral quality that is different 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.”
Non-fundamental 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 different levels, is
perceived as a sound. The level relationships between these sonic elements change
over time (controlled by envelopes, as described in Amplifier 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
reflected vertically, with taller spikes indicating higher levels.
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.