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4–5: String Main
4–5a
4–5b
4–5a: Excitation
The Excitation is the force that makes the string start to
vibrate. For a physical string, this might be a guitar pick, a
fingernail, a hammer on a clavinet, a plectrum on a
harpsichord, and so on.
Position
This models the position of the excitation (such as the pluck)
along the string, which has a strong effect on the timbre.
Important: the Tone parameter, below, must be non-zero in
order for Position to have any effect.
0.0 is one end of the string, at the bridge; 100.0 is the other
end of the string, at the nut (just before the headstock).
Usually, values between 8.0 and 25.0 should work well.
50.0 is the middle of the string. The timbres of different
values are approximately symmetric around this position,
except for very near the ends of the string. In other words,
60.0 produces a similar timbre to 40.0, 75.0 is similar to
25.0, and so on. The delay between the excitation and the
pickups will change, however.
Excitation Position
Position = 0.0
Harmonic structure with Position = 20.0 (ratio = 1/5)
How Position affects the timbre
Depending upon the Position, some overtones will be
emphasized, and others de-emphasized. At specific
positions, certain overtones will disappear completely, as
detailed below.
You can also think of the Position as a fraction of the total
string length. For instance, 50.0 means that the excitation is
[0...100.0]
half-way along the string; 33.3 means that excitation is 1/3
of the way along the string; 25.0 is 1/4 of the way along the
string, and so on.
Reaching back into math class for a moment, the number
under the fraction is called the denominator. For instance,
the denominator of 1/5 is 5.
As a rule of thumb, harmonics which are multiples of the
denominator will be silent. For instance, if the Position is set
to 20.0, the ratio is 1/5, and so every fifth harmonic will be
silent: 5, 10, 15, etc. This is like a comb filter, with
successive, evenly-spaced notches.
The graphic below shows the shape of this comb filter, and
the resulting basic harmonic structure. (Comb filters are
named because their shape looks a little like the teeth of a
comb.)
Position = 100.0
PROGRAM > STR-1: String 4–5: String Main
4–5PMC
4–5c
4–5d
221
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