Modulation and Envelopes

Modulation is how a patch changes over time. A modulation source produces a moving control signal, and you route that signal into a control input somewhere else in the patch.

Most modulation sources output control signals, usually in a 0 to 1 or -1 to +1 range. Match that range to the destination with Map Range when they differ. See Data Types and Conversion for why range and unit matter.

Envelopes

An envelope is a one-shot shape triggered by a note. Use ADSR for the classic attack, decay, sustain, release contour.

• The Gate input accepts MIDI, gate, or trigger, so you can drive it straight from MIDI Input or from a MIDI Decode gate.
• The Velocity input scales the output by how hard the note was played.
• Attack and Decay run from 0 to 10 seconds, Release from 0 to 30 seconds, and Sustain is a 0 to 1 level.
• The Envelope output is a 0 to 1 control signal.

The most common destination is amplitude. Send the envelope to the Gain input of a VCA so the note fades in and out instead of droning.

Editing on the Display

The ADSR display is a live control, not a picture of the settings. It carries four handles — one per stage — and dragging a handle sets that stage directly. This is usually faster than the sliders.

There is no single Curve control. Each stage carries its own curve amount running from -1 (ease-out) through 0 (linear) to +1 (ease-in), and curve is edited only on the display.

Alt-drag a segment to bend it. The cursor changes over a bendable segment. Bend the attack for a snappier or softer onset, the decay for a different fall, the release for the tail.

LFOs

An LFO is a free-running cyclic source for vibrato, tremolo, and slow sweeps.

• Waveform picks sine, triangle, saw up, saw down, square, or sample-and-hold.
• Rate sets the speed in Hz; the Rate input lets another signal modulate it. Patch a Clock Divider output into Rate to lock the LFO to musical divisions instead of free Hz.
• Polarity chooses bipolar (-1 to +1) or unipolar (0 to +1). Bipolar swings above and below the centre; unipolar only adds.
• Depth attenuates the raw modulation signal. Use Map Range when you need a specific output window or destination unit.
• The Reset trigger restarts the phase, which is useful for syncing the LFO to a note or clock.

Drawn Shapes

Shaper plays a shape you draw, so modulation is not limited to the LFO waveforms. Draw the curve once and it becomes a reusable Shape asset that outputs an ordinary control signal.

• Rate takes a speed in Hz, or a Clock Divider phase output for synced cycles.
• Reset restarts the shape at phase 0.

Reach for it when you want sidechain-style ducking, a rhythmic gate, a custom tremolo, or any automation curve that would be awkward to build from an LFO and math nodes. Because the shape is visible on the node, the intent stays readable in the patch.

Other Modulation Sources

• Random produces a new random value each time its Trigger fires, bounded by Min and Max. Good for per-note variation.
• Sample & Hold samples its input on each trigger and holds that value until the next one. Feed it noise or an LFO for stepped, stair-step modulation.
• Slew Limiter smooths a signal by limiting how fast it can change. Use it to soften a jumpy controller.
• Glide smooths a control signal toward each new value over a single Time constant. This is the portamento node: put it between a MIDI Decode pitch output and an oscillator Pitch input and notes slide instead of jumping. It does not change the target range.

Common Patch Examples

Amplitude envelope

This turns the droning oscillator from Getting Started into a played note.

1. MIDI Input MIDI Out → ADSR Gate.
2. ADSR Envelope → VCA Gain.
3. Oscillator Signal → VCA Signal → Audio Output Audio In.

graph LR
    MIDI[MIDI Input] -->|Gate| ADSR[ADSR]
    ADSR -->|Envelope| VCA[VCA]
    OSC[Oscillator] -->|Signal| VCA
    VCA -->|Audio| OUT[Audio Output]

LFO filter sweep

1. LFO Signal → Map Range into a useful cutoff span, for example 200 Hz to 2000 Hz.
2. Map Range output → Filter cutoff.

graph LR
    LFO[LFO] -->|Signal| MAP[Map Range]
    MAP -->|Cutoff| FILT[Filter]

Set the LFO to unipolar if you only want the cutoff to rise from a base, or bipolar to swing around a centre.

Stepped random pitch

1. A clock or LFO trigger drives Sample & Hold.
2. Feed Sample & Hold a changing source on its input.
3. Send the held value through Map Range into an oscillator pitch input.

graph LR
    TRIG[Clock / LFO] -->|Trigger| SH[Sample & Hold]
    SRC[Changing source] -->|Input| SH
    SH -->|Held value| MAP[Map Range]
    MAP -->|Pitch| OSC[Oscillator]

Rules of Thumb

• A source produces movement; a destination is the control input you route it into.
• Use an ADSR into a VCA for amplitude. Use an LFO for repeating motion.
• Match range and unit at the destination. Reach for Map Range when they differ.
• Bipolar modulation swings both ways; unipolar only adds. Pick the one the destination expects.
• Use Slew Limiter to smooth, Sample & Hold to step, Random to vary, and Glide for portamento.
• The ADSR display is editable. Drag a handle to set a stage, Alt-drag a segment to bend it.
• Reach for Shaper when no LFO waveform fits the movement you want.