Frap Tools CGM, Manual, Page: 8 / 107

Rev. 7 – Aug 2021 Page 8 of 107
MODULAR SYNTHESIS: CORE CONCEPTS
In this introduction we’ll go through the basics of ana-
log modular synthesizers in their broader meaning, to
make sure that all the technical jargon that we’ll be inev-
itably using throughout the manual will be, hopefully,
clarified for the newcomers.
Modules in a modular synthesizer can be thought of as
strangers sitting next to each other on a train compart-
ment, sitting in an embarrassed silence.
Creating music from a modular synthesizer is like start-
ing a conversation on our hypothetical train compart-
ment, by connecting modules with patch cables and mak-
ing them “speak” to each other.
For any conversation to happen we need two things: the
people must have something to say (like an argument),
and they must speak the same language.
In modular synthesizers, the argument is your musical
idea, and it is beyond the scope of this manual, while the
common language to make your modules communicate
is the
voltage
.
1
VOLTAGE (AND CURRENT)
Even though this is not an engineering manual, a gen-
eral introduction on the concept of voltage might be use-
ful to better understand how these instruments work.
Voltage is the difference in electric potential between
two points of a circuit, or, oversimplifying, «what you ap-
ply to cause currents to flow.»
1
It is measured in volts,
whose symbol is V. Without any other specification, the
voltage is calculated between any point of the circuit and
a reference point called ground (0 V).
Electric potential brings in the concept of current , which
is the actual flow of electric charge through a circuit.
Electric charge is measured in coulomb (C), while the
current is measured in amperes (A): 1 ampere equals to 1
coulomb of charge passing through a given point in 1 sec-
ond.
Enough for the technical stuff: now it’s time to see how
voltage and current turn into (electronic) music.
2
DC AND AC
There are two kinds of current, each of which implies a
different kind of voltage. They are direct and alternating cur-
rent, abbreviated DC and AC respectively, and we use
both in modular synthesizers.
In case of direct current, our charge flows only in one
direction: if the current is steady, so will do the voltage.
This kind of fixed voltages are what we use, for example,
to send note information to the sound source.
1
(Horowitz 2019, 1, note 2.)
In case of alternate current, our charge flows back and
forth in our circuit. Its alternation over time can be dis-
played with a waveform diagram. In case of alternate cur-
rent, the voltage changes over time as well. We use this
kind of varying voltages to generate, for example, wave-
forms that ultimately will turn into sound.
3
AUDIO AND CV
To hear music, we need some vibrating air. To make
the air vibrate, we need a vibrating body: we can pluck a
string, hit two wood sticks, blow into a pipe and so on.
In case of electronic instruments, our vibrating body is
the loudspeaker (or the headphones).
More in detail, in the specific case of analog modular
synthesizers, everything, from the sound generation, to its
articulation, to the final audio output through the speaker
cone’ vibration, is achieved through voltage that change
over time.
With our modular synthesizer we create a complex,
electric signal that makes our cones move back and forth.
The variation of voltage over time translates into the
complex waveform that we call music.
It goes without saying that the more control we have
over our voltage, the more expressive and articulated will
become our composition’s waveform.
In modular synthesizers, we use voltage to generate
sound, but also to control it.
If a circuit generates a voltage that varies from, say, -
5 V to 5 V, 110 times a second, it will make our loud-
speaker vibrate as many times, thus producing a sound
whose frequency is 110 Hertz (Hz), corresponding to the
note A.
However, if the same circuit generates a voltage oscilla-
tion of 10Hz, meaning that the voltage varies from -5 to
5 V ten times a second, we wouldn’t be able to hear it
anymore. It’s because its frequency is below our audible
range of human beings, that spans from 20 to 20.000Hz.
This brings in a conventional distinction between volt-
ages that we use for sound generation , which provide alter-
nate current in the audio range, and voltages that we use
for sound modulation or control , which are often called con-
trol voltages , or CV. Generally speaking, we use CV to turn
our modules’ knobs for us, in a sort of automated way.
CVs can be of any kind: they can generate alternate
current, such as low-frequency oscillators (LFOs, like the
ones we use for tremolo effects) or direct current (like the
fixed CVs that we use to send pitch information).