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Modulation adds movement to your sound by changing controls over time. Just like the basic signal flow of the synthesizer, you build modulation in your patch by loading and connecting specific Blocks.

What is Modulation?

Blocks used for modulation produce slowly changing signals that cannot be heard directly. These modulation signals are called CV (Control Voltage) on analog modular synthesizers.

When you apply modulation to controls in your patch, the controls change their value according to the shape of the modulation signal.

The most basic building block for modulation in synthesizers is the envelope. When triggered by a note event, the envelope produces a single contour that can be used to change controls over the course of a note.

A common type of envelope is the ADSR, named after the stages of its contour (Attack, Decay, Sustain, Release). In the subtractive synthesizer you can use it to control the volume level of the sound, for example. This is done by applying the modulation from the envelope to the VCA.

Adding an Envelope

You can use the search box to find the envelope and load it into the Rack.

Press the Enter key on your computer keyboard to open the search box. Type in "adsr" to find the Block called Bento Box ADSR and load it by pressing the Enter key again.
Move the Bento Box ADSR between Util Note In and Bento Oscillator.
The Bento Box ADSR needs to be triggered by new note events. For this purpose, the Util Note In sends an event (called gate) from its GATE output. When the Bento Box ADSR receives this gate event, it starts to produce its contour.

Connect the GATE output of Util Note In to the GATE input on Bento Box ADSR.

Connecting Modulation

To modulate controls in your patch, the relevant Blocks need to be connected first. Each Block provides two general inputs for modulation called A and B.
  • Connect the OUT of Bento Box ADSR Envelope to the A input of Bento Box SVF.
  • Then connect the OUT of Bento Box ADSR Envelope to the A input of Bento Box VCA.

Routing modulation

The modulation connected to the A and B ports can be routed to any of the Block’s controls. You can show the modulation routing by using the A and B buttons on the top-right corner of each Block.
  • Click the A button on Bento Box SVF to show its modulation routing.
  • Then click the A button on Bento Box VCA to show its modulation routing.
The sliders appearing next to controls set the modulation amount. This determines the strength of the modulation applied to the control.
  • Move the slider next to CUTOFF on Bento Box SVF fully up.
  • Then move the slider next to LEVEL on Bento Box VCA fully up.
Now the envelope is set up to control the timbre and the volume level of the sound. In the next step, you will learn how to play the synthesizer and adjust the sound.

Note: Make sure the CUTOFF and LEVEL controls are turned down, otherwise the modulation will not work as intended.