How to use the FM synth

What is FM synthesis?

FM stands for frequency modulation and it’s when you take simple waveforms and modulate the frequencies with other simple waveforms. This is done using waveforms of different frequencies and amplitudes to kind of mangle, distort, and change the sound into something more complex and interesting. Compared to subtractive synthesis, FM synthesis can feel a lot more complicated. However, once you understand how it works, it can open a lot of doors to the magical world of sound design.

Adding FM synth presets [Beginner]

1. 1
   Open Soundation and create a project
2. 2
   Click on Instrument presets in the Sound library
3. 3
   Search for “FM synth”
4. 4
   Drag in a preset to the Arrangement area
5. 5
   Start playing or drawing in notes

Making FM synth sounds [Pro]

1. 1
   Open Soundation and create a project
2. 2
   Click on Add channel and add an Instrument channel
3. 3
   Change the instrument to FM synth in the Bottom panel
4. 4
   Click on Edit FM synth to open the instrument
5. 5
   Start tweaking the settings to your liking

Operators

The FM synth has six Operators. If you’re used to subtractive synthesis, you could think of these as oscillators.

Each Operator produces a sine-wave that can be either a Carrier or a Modulator. A Carrier is something you can hear. You can’t hear a Modulator directly. Instead, it is used to change the tone/color/timbre of the Carrier.

Algorithms

Whether an operator is a Carrier or a Modulator is decided by the Algorithm setting. Operator number 1 is always a carrier. Then each algorithm connects the rest of the operators in different configurations as carriers or modulators.

Here is a schematic of all the different algorithms:

The bottom row shows the carriers while the rows above show the modulators. Let’s take algorithm 1 as an example. Operators 1 and 3 are Carriers that produce sound. Operator 2 is a Modulator that modulates operator 1. Operator 6 is modulating operator 5, which is modulating operator 4, which is modulating operator 3. Operator 6 can also modulate itself, which you can see in the schematic above by the looped line around the box.

Feedback

All algorithms in the synth will have one operator connected with a feedback loop. This means the operator output is connected back into itself and modulates itself. Increasing the Feedback will produce a brighter and more harmonic sound, or in some cases, distortion or noise.

Ksync

Ksync or key sync affects all operators globally and turning it on will force all sine-waves to start in phase with each other. If it is turned off there will be slight variations with each new note, which will give some tonal differences. If you want a more consistent sound, turn Ksync on.

Level

For each operator, you can control its volume using the Level knob. For Carriers, the Level knob controls how loud it is. For Modulators, the Level knob controls how much it modulates the operator it is connected to. The more you turn up the Level of a Modulator, the brighter and more complex the sound of the Carrier will be.

Velo

Velo sets the operator's level sensitivity to your keyboard velocity or note velocity. It’s common to increase the Velo on Modulators. If you do, the harder the note, the more complex and bright the sound will be. When played with different velocity levels, this will provide a lot of expressiveness.

Frequency settings

The frequency settings of each operator decide its pitch. Control the pitch with the Coarse, Fine and Detune parameters.

If Fixed is unchecked, the pitch will be in Ratio mode and follow what you play on your keyboard.

With the Ratio mode active the Coarse setting is divided into 32 steps, each equal to the natural overtone series. The settings represent different frequency ratios. Starting from 0 to 31, where 1 is the fundamental frequency and 0 is one octave below it.

Fine divides the pitch further into 100 smaller steps, from 00 to 99.

Detune divides the pitch up further into 15 subdivisions, ranging from -7 to +7.

If Fixed is checked the operator will instead play a fixed frequency. This is usually most useful if the operator is a modulator. In Fixed mode, you can set the frequency between 1Hz and 9,772Hz using the Coarse and Fine settings.

Envelopes

The envelopes in the FM synth are different from our other instruments which use ADSR envelopes. Although more complicated, it’s also less restrictive. You control the envelopes with rates and levels using the knobs labeled R1 to R4 and L1 to L4. Each knob can be set between 0 and 99.

Each L knob is like a checkpoint where you set either the level of the amplitude or modulation at that specific point. If an operator is a Carrier, the envelope will affect the amplitude. If an operator is a Modulator, the envelope affects the tone and timbre of the sound.

The corresponding R knob is the rate, or how fast the operator reaches that level of the L knob. A low rate means it will be a slow change and a high value means it will be a fast change.

R1 is similar to Attack on an ADSR envelope, it controls the time it takes to get to the level of L1.

When the level has been reached, it will move to L2 at the speed of R2.

When the L2 level has been reached it will then move to the level of L3, at the speed of R3.

When the L3 level has been reached it will then maintain this level for as long as you hold down the note. L3 here is the same as Sustain in normal ADSR envelopes.

When you release the note, it will move to the level of L4 at the speed of R4. This means R4 is similar to the Release in an ADSR envelope. Be careful with the L4 value however. A Carrier at a value higher than 0 means it will sustain forever. Usually, this is only useful for operators that act as Modulators.

Pitch envelope

The Pitch Envelope is a global envelope used to modulate the pitch of all operators. This envelope works mostly the same as the ones we find in the operators.

The difference is that L1-L4 knobs control the amount it pitches up or down. When centered at 50, there is no change in pitch. A value lower than 50 means a lower pitch and a value higher than 50 means a higher pitch.

The Rate knobs once again control the time it takes for the pitch to change from one pitch level to another.

Scaling

The Scaling part of the synthesizer allows you to create a loudness curve for each operator across the range of the keyboard. This can be used for effects like split keyboard functionality. More subtly, it can be used to create different loudness curves on the left and right-hand sides of the keyboard. For example, the curve can allow you to raise the level of one operator on the right-hand side of the keyboard.

To see the scaling options, make sure to click on the Scaling tab.

Rate defines the decay for each operator’s envelope depending on where on the keyboard you play. With a value of 0, the decay is the same across the full range of the keyboard. Higher values will make the lower notes decay slower than the higher notes, which will decay faster.

Break or breakpoint defines the center point for the operator on your keyboard. On either side of the breakpoint, you have different loudness Curves and Depths.

Depth defines the amount of scaling for your right and left-hand sides of the keyboard. 0 is the center value and depending on the curve you choose 99 will be either a positive or negative value.

Curve sets the curve type of the keyboard scaling.

0 = -LIN (negative linear curve)

1 = -EXP (negative exponential curve)

2 = +EXP (positive exponential curve)

3 = +LIN (positive linear curve)