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GENERATORS
Sytrus Tutorial Property in Barcelona
FM Synthesis is typically regarded as black magic by most
amateur synthesizer programmers. The Yamaha DX-7, the first popular
FM synthesizer, was reported to have 90% of maintenance returns
complete with their presets intact. You have probably browsed
through the presets in Sytrus, and wondered, “how did they do
that?”. The next step, then, is usually to search the Internet for
FM synthesis tutorials, only to discover that most of them tell you
how to program a Yamaha DX7, or a particular DX7-like FM
synthesizer to achieve a handful of particular sounds. But there's
no clear idea how those "FM fundamentals" apply to Sytrus'. This
tutorial will help remove some of the mystery from FM synthesis in
general, and help you on your way to understanding what all those
mysterious controls and knobs in Sytrus do.
Operators, Modulation Matrix, or Filters.
This tutorial is all about the Sytrus FM synthesizer, and the
purpose behind the most important controls on its variety of
control panels. This tutorial will not discuss each knob and
slider, and how each individual control affects the output signal.
However, after proceeding through this tutorial, you will
understand:
- What an "operator" is.
- How the modulation matrix is configured to route sounds from
the oscillators through the modulators, filters, and effects
processing to the output.
- How to apply a filter to an operator.
- The single difference between FM and subtractive synthesis
Step 0: Learn about subtractive synthesis basics
It's fairly easy to get a basic grip on FM synthesis. Starting
with simple waveforms, filters and envelopes are applied to get
different "effects" on the final sound. With most subtractive
synthesizers, you can pick a knob at random, tweak it, and likely
hear a difference in the sound that comes out as a result. The
3xOSC or TS404 plugins are a good place to start out. Once you're
comfortable with terms like, "oscillator", "LFO", "cutoff", and
"ADSR", you may proceed.
Step 1: Understand what you're looking at in Sytrus
- 1.1 Add a Sytrus channel. Click the "plug" in
the upper left of the window, and select the "Default" patch. This
patch produces a pure sine wave output. Ignore the 9x9 matrix
control on the right side of the window for now.
- 1.2 Click the "MAIN" box in the upper left to
see how the synthesizer's overall characteristics are defined.
These parameters operate on the signal that comes out of the
synth/filter/pan/fx module. You can apply an overall volume and
filter envelope, tweak the basic EQ, add a unison effect, and
determine which parameters are affected by the x/y modulation
controls.
- 1.3 Click on the "OP 1" box towards the top of
the window. This panel defines "Operator #1". An operator is simply
a waveform; some audio signal. You can see one cycle of it in the
box in the upper left. The sliders and knobs to the right of the
waveform display allow you to modify some characteristics of the
waveform. The row of buttons, "PAN", "VOL", etc. allow you to
modify the characteristics of the waveform. "OP 2" through "OP 6"
allow you to define five more waveforms.
- 1.4 Click on the "FILT 1" box towards the top
of the window. This panel defines "Filter #1". The panel and rows
of buttons allow you to specify the characteristics of a filter,
which can be applied to the output of the operators. "FILT 2" and
"FILT 3" allow you to define two more filters.
- 1.5 Click on the "FX" button towards the top
of the window. This panel defines a basic effects chain consisting
of panning, chorus, three delay units, and reverb.
Step 2: Sytrus, the Subtractive Synth, part 1 - The Sawtooth
Wave
As a first step in learning how to program the Sytrus synthesizer,
we will examine its capabilities as a subtractive synthesizer. This
will build on our knowledge from Step 0, above, as we start to
learn how to find our way around Sytrus without getting too
complicated.
- 2.1 Go back to the "OP 1" panel, and slide the
"SH" slider (just to the right of the waveform display). As you
slide it up, the waveform will change from a sine wave through
triangle, saw, and square patterns, ending up with a square pulse.
Set the slider in the middle of its range (50%) to produce a
sawtooth wave. Play some notes and listen to the buzzing of all the
high frequency components in the sawtooth wave.
- 2.2 Now we'll take a look at the modulation
matrix. In the Default preset, only one knob is activated. On the
far right of the OP1 row, the knob in the "OUT" column is turned
all the way up, to 100%. This knob indicates that the output from
OP1 should go straight to the output at full volume. Each of the
top six knobs in the "OUT" column indicate how loud each of the
operators should be in the output mix. The bottom three knobs
indicate how loud the output from each filter should be in the
output mix.
Step 3: Sytrus, the Subtractive Synth, part 2 - a basic filter
envelope
- 3.1 Now, we'll apply the default filter to the
saw wave in operator 1. First, right click the OP1 output level
knob to mute it. Play some notes. Note that there is now no output
from Sytrus. At least one of the various output knobs must be
turned on to generate any output. So, to activate the output of
filter 1, turn the output knob on the F1 row up to 100%. Play some
notes. Note that there is still no output from Sytrus. At this
point, we're sending 100% of the output from the filter to the
output. However, there's no input signal to the filter, so no sound
will be generated.
- 3.2 To send some of the OP1 signal to the
first filter, turn on the knob in the first column of the F1 row,
and set it to the full on position, 100%. This sends the output of
OP1 to the first filter. The output knob in the F1 row sends the
output of the first filter to the output module. Play some notes.
The default filter, applied to the saw wave produces a cheap synth
horn sound.
- 3.3 Activate the cutoff envelope for the first
filter. Click on the "FILT 1" button toward the top of the window.
This displays the Filter 1 settings. Click the "CUT" button in the
middle row of buttons. This displays the parameters for the filter
cutoff envelope. Click the "ENV" button to display the default
envelope. Just under the bottom of the graphical envelope display
are four knobs to set the Attack, Decay, Sustain, and Release
parameters of the envelope. To the left of these four buttons, is a
small, hollow radio button. The default setting is "off",
indicating no filter cutoff envelope should be applied. Click the
radio button to activate the filter cutoff envelope. Play some
notes. Note how the cutoff envelope alters the sound of the "horn".
Experiment with the ATT, DEC, SUS, and REL knobs to see how they
alter the sound of the wave.
Step 4: An Introduction to Modulation
The modulation operation: Basically, two waves combine in a magic
way to create a richer spectrum output. It is important to note
that OP1 modulating OP2 (OP1*OP2) does not produce the same output
as OP2 modulating OP1 (OP2*OP1). Well, it's not that important, but
just know that tweaking the OP1/OP2 modulation parameter will
result in a different output than tweaking the OP2/OP1 modulation
parameter.
Step 5: Sytrus, the FM synth, Simple Modulation
Step 6: Filtering a modulated signal
- 6.1 Now, we'll apply the filter we created
above to the FM modulated signal. Deactivate the OP1 output by
right clicking on the OUT/OP1 knob. Make sure the OUT/F1 knob is
activated. If not, right click it to activate it. Activate the
OP2/F1 knob by turning it to 100%. Play some notes. The sound will
be that of a pure sine wave. What's going on here?
-
Well, what we actually did is route OP2 (an unmodulated sine
wave) into Filter 1. Operator 2 is still at its default setting of
a sine wave, so the output generated is a filtered sine wave, or,
in other words, a sine wave. What we wanted to do is send OP1 into
Filter 1. (This may be the most confusing feature of the modulation
matrix itself.) This is part of what I mean by OP1*OP2 not being
the same as OP2*OP1. Since we configured OP2 to modulate OP1, in
order to send the modulated OP1 output to a filter module, we must
use the OP1 column of the desired filter row to route that signal
accordingly.
- 6.2 To route OP1 into Filter 1, deactivate the
OP2/F1 knob by right clicking on it, and re-activate the OP1/F1
knob by right-clicking on it. Now, we are routing the modulated OP1
signal into the filter. Play some notes. Now, the filter we created
above is acting on the modulated signal.
Step 7: The single difference between FM and Subtractive
synthesis
Subtractive synthesisuses richer waveforms
(triangle waves, square waves, etc.) as the base signal before
applying filtering, resulting in higher order harmonic content in
the synthesized signal. FM synthesiscreates richer
waveforms via modulation, resulting in "sidebands" of the carrier
signal (i.e. the operator being modulated). That's it. Both use
filters, envelopes and modulators on the sound. Once you understand
what the knobs in the modulation matrix do, you're off and running.
FM Synthesis can seem intimidating because it does not seem as
intuitive as basic subtractive synthesis. The “sidebands” resulting
from the modulation operations are not as easily visualized as
relatively simple square waves, or triangle waves. Also, FM
synthesizers typically have much more complex envelopes and
automation capabilities (see the “Electrocution” preset for a
complex automated filter example), adding to their complexity and
intimidation factor.
Tutorial credits:Eric Mitchell.
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