FL Studio Sytrus Tutorial: FM Basses, Bells and Keys

What is Sytrus and what can it do?

Sytrus is a synthesizer built around six operators (oscillators) that can do FM, ring modulation, subtractive and additive synthesis. It adds three filter modules with 13 filter modes each, plus a chorus, three delay lines and reverb^[1]. It is included from FL Studio Producer Edition up^[2].

The one thing that confuses new users: neither the operators nor the filters make sound on their own. You have to route them to the output in the modulation matrix^[1]. If a patch is silent, the matrix is the first place to look.

This tutorial is Sytrus-specific. For FM theory on its own (carriers, modulators, sidebands) read the FM synthesis beginner's guide first, then come back and apply it here.

How does the Sytrus modulation matrix work?

Each row of the matrix is an operator, and the knobs in that row decide which operators modulate it and by how much. A knob on the diagonal (for example row 2, column 2) makes an operator modulate itself, which creates feedback^[1].

Beyond the FM grid, separate columns send each operator to the three filters, to pan, to the effects and to the main output. A negative output value sends an inverted signal^[1]. An FM/RM switch changes the grid from frequency modulation to ring (amplitude) modulation.

Why you cannot automate the FM knobs

The FM and RM matrix knobs cannot be automated. The manual's workaround is to automate or modulate the modulator's Volume (VOL) knob on its operator page, which has exactly the same effect because it changes the amplitude, and so the amount, of the modulation^[1]. Every patch below relies on this: the modulator's volume envelope is your brightness envelope.

Which operator ratios and envelopes matter most?

The modulator's frequency ratio sets the character, and the modulator's volume sets the brightness. In Sytrus, Frequency Ratio multiplies the base pitch: x2 is an octave up, x0.5 an octave down, and Frequency Offset adds an absolute shift in Hz^[1].

Whole-number ratios between carrier and modulator give harmonic, pitched tones, and non-integer ratios give inharmonic spectra like those of bells and many percussion instruments^[3]. The modulation index, which in Sytrus you control with the modulator's volume and its matrix knob, decides how many sidebands have real energy: more index, more brightness^[4].

• Modulator VOL envelope The brightness over time. Fast attack and short decay give a pluck. Slow attack gives a swell.
• Carrier VOL envelope The loudness over time, like a normal amp envelope.
• MOD envelope Sets how much influence incoming modulators have on this operator^[1]. Use it on the carrier when one modulator feeds several carriers.
• ADSR sliders Each envelope has attack, decay, sustain and release controls, sustain loop points and tempo sync^[1].

How do you set up a clean Sytrus patch from scratch?

Load the Default preset so every control is reset, then build a two-operator stack: operator 2 modulates operator 1, and only operator 1 reaches the output. The manual recommends starting from Default for exactly this reason^[1].

1. Load Default
   Open the Sytrus preset menu and pick Default.
2. Check the output column
   Make sure operator 1's output knob is up and operators 2 to 6 are at zero, so you only hear the carrier.
3. Route the modulator
   In the FM grid, turn up the knob in row 1 under column 2. Operator 2 now modulates operator 1.
4. Set shapes to sine
   Keep both operators on sine while learning. Sine into sine makes every change easy to hear.
5. Play and sweep
   Hold a C3 and slowly raise operator 2's volume. The tone moves from pure sine to bright and buzzy.
6. Save the init
   Save this as your own FM init preset so each new patch starts from the same point.

How do you make an FM bass in Sytrus?

Use a 1:1 ratio with a short modulator envelope, so each note starts bright and settles into a round, sine-heavy body. That shape gives a punchy attack that cuts through on small speakers while the sustain stays clean for the sub.

1. Start from your init
   Operator 2 into operator 1, both sine, ratio x1 on both.
2. Shape the modulator
   On operator 2's VOL envelope, use near-zero attack, a decay around 150-300 ms and sustain around 20-30%. Adjust by ear.
3. Add a sub layer
   Send operator 3 at ratio x0.5 to the output at low level for weight. Keep it a pure sine with no modulation.
4. Add grit carefully
   Turn up operator 2's diagonal feedback knob a little for a growl. Too much turns into noise.
5. Make it monophonic
   In the channel settings, enable Mono so only one note plays at a time, and Porta with a short Slide time for glides between notes^[5].

Check the bass in mono and against the kick. The full low-end process, including tuning, is in how to make 808 bass in FL Studio from scratch.

How do you make bell sounds in Sytrus?

Use a non-integer modulator ratio, a modulation amount that falls from bright to pure, and a long exponential volume decay. That combination is the classic FM bell recipe described in the Cycling '74 FM tutorial^[4]. Real bells need more than one pair, because their partials sit at clearly non-integer ratios to the fundamental^[3].

1. Set an inharmonic ratio
   Put operator 2 at a ratio like x1.41 or x3.14 and route it into operator 1. Avoid simple halves like x3.5, which still land on a harmonic series one octave down.
2. Shape brightness
   Give operator 2 an instant attack and a decay of 1-2 seconds with zero sustain, so the metallic top fades first.
3. Shape loudness
   Give operator 1 an instant attack, a 2-4 second decay and zero sustain, with a matching release so notes ring out.
4. Add a second pair
   Route operator 4 into operator 3 with a different ratio, around x2.76, and mix operator 3 in quietly for extra partials.
5. Place it in the mix
   Play in the upper octaves, add a little reverb, and high-pass the low end so the bell sits above the 808.

For trap melodies built from these sounds, see how to make trap bells and plucks.

How do you make electric piano and keys sounds in Sytrus?

Use a harmonic ratio that is very slightly detuned, with a quick modulator decay for the attack "bark" and a longer carrier decay for the body. The Cycling '74 tutorial uses a slightly mistuned harmonic ratio for its electric piano preset^[4].

1. Body pair
   Operator 2 at ratio x1 into operator 1. Nudge operator 2's Frequency Offset by 1-2 Hz for a gentle beating.
2. Tine pair
   Route operator 4 at a high ratio, around x14, into operator 3 at x1, with a very short modulator decay of 30-80 ms. Mix operator 3 low.
3. Link velocity to tone
   Map velocity to the modulators' volume so harder hits sound brighter, the way a real electric piano does.
4. Tame the top
   The manual advises checking higher notes for aliasing in FM patches and reducing modulator levels with keyboard mapping^[1]. Draw the key mapping to fall off above C6.
5. Finish with chorus
   Send a little of the output to the Sytrus chorus for width.

Sytrus keys also layer well under sampled pianos. Stack the FM tine on a soft piano and each covers the other's weak spot; how to layer synths explains the EQ side of that.