Parameter Modulation System

The modulation routing system — LFOs, envelopes, and macro controls

Any modulatable knob in k2k can come alive. Instead of sitting at a single fixed position, a parameter can follow a drawn curve, ride a repeating oscillator, or track an external envelope from somewhere else in your graph.

You access modulation by right-clicking any knob with a lavender highlight — that color marks every modulatable parameter. A context menu appears with the available modes.

All modulation swings around the knob’s current static value. The knob sets the center point; modulation pushes the value above and below that center. Depth controls how far the swing reaches. If a parameter has a custom modulation range set, the swing stays within that range rather than spanning the full parameter limits.

Static

What it does — The parameter sits at a fixed value. This is the default state for every knob. You turn it, it stays where you put it.

No additional parameters. The knob value is the output value.

Curve

What it does — Draws keyframe automation that plays back over time. You place points on a curve editor, and the parameter follows that shape as your audio plays. Interpolation between keyframes is smooth (spline-based), so even a few points produce fluid motion.

When you’d reach for it — You want a parameter to change in a specific, deliberate way over the duration of your audio. A filter cutoff that opens during a vocal phrase. A gain fade at the end of a section. Any movement that needs to happen at exact moments.

Quick example

Right-click a filter cutoff knob and choose Add Curve Modulation.
The curve editor appears in the viewer, showing a flat line at the knob’s current value.
Click to add a keyframe at the start of the vocal phrase, drag it down to roll off highs.
Add a second keyframe where the phrase peaks, drag it up to open the filter.
Add a third keyframe at the phrase end, bring it back down. Play back to hear the sweep follow your shape.

Parameters

Parameter	What it controls	Range
Curve Editor	Visual keyframe editor — click to add points, drag to move them, right-click to delete	Timeline matches audio duration
Time Mode	How the curve maps to your audio: Extend holds the last value beyond the curve’s end; Loop repeats the curve cyclically; Normalized stretches or compresses the curve to fit the audio length	Extend / Loop / Normalized
Mod Range	Custom swing range around the static value — when set, the curve operates within this range instead of the full parameter limits	Depends on parameter (e.g. +/-12 dB for a gain knob)

LFO

What it does — A repeating oscillator that continuously sweeps the parameter up and down. Choose a waveform shape, set the speed and depth, and the parameter wobbles on its own.

When you’d reach for it — You want ongoing, rhythmic movement without drawing anything. Tremolo on a pad. A slow filter sweep that never stops cycling. Vibrato-like pitch wobble. Anything that should pulse or breathe at a steady rate.

Quick example

Right-click a gain knob on a synth pad and choose Add LFO Modulation.
Leave the waveform on Sine for smooth tremolo.
Set Rate to 4 Hz for a fast, obvious pulse, or 0.5 Hz for a gentle swell.
Set Depth to 50% — the gain now swings halfway between its limits on either side of the knob position.
Shift Phase Offset to 50% if you want the oscillation to start at the opposite point in its cycle.

Parameters

Parameter	What it controls	Range	Default
Rate	Oscillator speed in free-running mode	0.1 - 20 Hz	1 Hz
Rate Mode	Whether the LFO runs at a free Hz rate or locks to the project tempo	Hz / Tempo Sync	Hz
Tempo Division	Musical subdivision when in Tempo Sync mode	Whole, Half, Quarter, 8th, 16th, 32nd, 64th, Quarter Triplet, 8th Triplet, 16th Triplet	Quarter
Waveform	Shape of the oscillation	Sine / Triangle / Square / Saw	Sine
Depth	How far the parameter swings from its center value	0 - 100%	50%
Phase Offset	Starting position within the waveform cycle	0 - 100%	0%

Sidechain

What it does — An external envelope from your graph drives the parameter. An Envelope Follower node analyzes an audio source and publishes its amplitude envelope to a named slot in the Envelope Registry. Any parameter set to Sidechain mode can then read from that slot and follow the envelope’s shape.

When you’d reach for it — You want one sound to control another. A kick drum’s envelope ducking a pad’s gain. A vocal’s dynamics shaping a reverb’s wet level. Any situation where the movement of one element should directly influence a parameter on a different element.

Publishing an envelope (the source side)

Place an Envelope Follower node in your graph and connect an audio source to its input (e.g., a kick drum).
In the Envelope Follower’s parameters, type a name in the Slot Name field (e.g., “Kick”). The node automatically claims a slot in the Envelope Registry.
Configure the follower’s detection mode (Peak or RMS), attack, and release to shape how tightly the envelope tracks the source dynamics.
When the Envelope Follower executes, it computes the amplitude envelope and pushes it to its registry slot. The slot is now live — any sidechain-modulated parameter pointing to it will receive this envelope.

Consuming an envelope (the destination side)

On a different node, right-click a modulatable knob and choose Add Sidechain Modulation.
Set the Slot number to match the Envelope Follower’s slot.
The parameter now reads the published envelope each time it evaluates — when the source gets loud, the envelope value rises; when it gets quiet, the value drops.
Use Depth, Offset, and Bipolar to shape how the envelope translates into parameter movement.

Quick example

Place an Envelope Follower after a kick drum source. Name the slot “Kick” — it auto-assigns to Slot 0.
Set the follower to Peak detection, Attack 1 ms, Release 100 ms for a punchy envelope that tracks each hit.
On a separate pad chain, right-click the Gain knob and choose Add Sidechain Modulation.
Set Slot to 0 so it reads the kick’s envelope.
Set Depth to -80% — when the kick hits, the pad ducks down. Between hits, the pad returns to its knob value.
Adjust Offset to fine-tune the resting level between kicks.

Parameters

Parameter	What it controls	Range	Default
Slot	Which envelope registry slot to read from (published by Envelope Follower or other analysis nodes)	0 - 15	None (pick one)
Depth	How strongly the envelope pushes the parameter — positive values follow the envelope, negative values invert it	-100% to +100%	100%
Offset	Shifts the envelope value up or down before applying depth, useful for biasing the modulation center	-100% to +100%	-50%
Bipolar	When on, the envelope is recentered so 50% becomes zero — values above 50% push positive, below push negative	On / Off	Off

How the envelope flows

Envelope Follower → analyzes audio → computes envelope → publishes to Registry Slot
                                                                    ↓
Any parameter (Sidechain mode) → reads from Registry Slot → applies Depth/Offset/Bipolar → modulates knob value

The registry holds up to 16 simultaneous envelopes. Multiple parameters across different nodes can read from the same slot — one kick envelope can duck several parameters at once.