Table of Contents
Advertisement
1. WELCOME
1.1. What is a modulation effect?
Modulation effects work by modifying the sound in a certain way, usually by means of
modulation controlled by a Low-Frequency Oscillator (LFO). For example, they can add one
or more slightly delayed versions of the sound to itself, while modulating the pitch of those
versions over time.
We can obtain three main effect types with modulation: chorus, flanging, and phase shifting.
Of these three, chorus is perhaps the most sought-after one, since it allows to create "richer"
versions of the sound. Chorus effect works by taking the audio signal and mixing it with
one or more delayed, pitch-modulated copies of itself. The pitch of the added voices is
modulated by an LFO, which makes the overall effect similar to that of the flanger, except
with longer delays and less modulation.
Flanger is an effect similar to the Chorus, produced by mixing two identical signals, with one
signal delayed by a small and gradually changing amount of time and modulated through
an LFO, which produces a characteristic undulating (sweeping) effect, but with a sound
resembling the result of a comb filtering. Speeding up the LFO accentuates the modulation
effect. As we said, the effect is similar to the Chorus, but here we use shorter delays for the
delayed signal.
The flanger effect can be controlled by other sources than the LFO. Also, part of the
signal is usually fed-back into the input, producing a resonance effect. The phase of the
feedback signal can also be inverted, to achieve further variations of the flanger effect.
Flangers usually make great use of feedback to receive more processing. This accentuates
the notches and resonances, resulting in the harsh, metallic timbre that is one noticeable
characteristic of flangers.
The Phaser (phase-shifter) is another modulation effect, with results somehow similar to
Flanger. It is produced by splitting the audio signal in two paths, one being treated by all-
pass filters, which preserve the amplitude of the original signal but alter its phase. Here, we
use no delayed signal. The absence of delays is the main difference between phase-shifters
and the other modulation effects. After the all-pass filtering, the two paths are mixed again,
and the frequencies that are out of phase will cancel each other, producing the phaser's
characteristic "whoosh" sweeping effect.
So, the phaser works by canceling bands of frequencies to obtain the desired effect (which
is something we already observe in the flanger, by the way). Again, no delay is used in this
effect, which differentiates it from the other two.
Modulation effects can create a huge range of sonorities, and the results may be perceived
as a fuller, richer sound. No wonder they have been used extensively since they appeared.
Also, they have been somehow an obligatory addition to almost any synthesizer and
electronic keyboard manufactured since the eighties.
2
Arturia - User Manual Phaser BI-TRON - WELCOME
Advertisement
Table of Contents
