Make your LEDs listen

Audio-reactive LEDs usually mean one of two things: a microphone effect that flickers at everything, or a pile of DSP settings that wants a weekend. What I wanted for my own rigs sits in the middle: pick a knob, tell it to follow the kick, shape how it moves, done.

That's how it works in Filament. Almost any numeric control can listen - an animation's speed, an effect's dry/wet, a blur radius, the master brightness. Click the control's modulation button, choose Audio reactive, and the fader grows two markers: the output range the sound sweeps between. A live dot bounces between them showing the exact value being applied, every frame. It's the same value your LEDs are getting.

The master bar carries a live input monitor of 32 bands. Pick the input device and enable reactivity once, in Settings → Audio. Both of those are per-machine settings.

I've long carried with me to gigs a Focusrite Scarlett and a selection of cables for hooking up to the mixer outs.

Picking what it hears

The audio panel starts from presets named after what you actually want - Kick, Bass Pump, Snare / Clap, Hat Shimmer, Mid / Vocal, Smooth Swell, Balanced (Full). Nine times in ten you pick the one named after the thing you want to follow and move on. The tenth time, you drag two handles across a live mini-spectrum and carve the band yourself.

Then you shape the response, and this is where it stops looking like a VU meter:

• Threshold gates out the quiet stuff - this is what makes a parameter react to hits instead of to the whole mix. If your mapping is always somewhere in the middle and never at rest, raise it until the quiet parts read as silence.
• Punch shapes the curve - above 1 sharpens peaks and pushes the floor down. If the hits don't feel like hits, this is the knob.
• Attack and Release decide whether the light snaps or breathes.
• Invert flips the whole thing - sometimes the best move is lights that duck when the drop lands.

At silence the parameter rests at the bottom of its range - no twitching. And if the audio device disappears mid-show, the spectrum zeros and the parameter settles at its minimum instead of doing anything dramatic. Plug it back in and the mapping recovers on its own.

Two quality-of-life things I use constantly. Copy/paste modulation from the right-click menu: dial in one kick band exactly how you like it, then paste it onto five more parameters instead of rebuilding it five times. And Bypass: park a mapping without deleting it - the manual fader comes back, the band and shaping stay saved.

When there's no band for it

The same modulation slot takes an Envelope / LFO instead: start from a sine, saw, square, or triangle, then click to add points, drag them, and click a segment to cycle it between linear, smooth, and stepped. Sync the cycle to bars, from 1/8 of a beat up to 8 bars, or run it on a free clock from 50 milliseconds to a minute. There's a loop, a ping-pong, and a one-shot mode with a trigger button, so an envelope can be anything from a strobe to a slow eight-bar swell to a manually-fired sting.

Envelopes lock to the same master tempo as everything else, the one that follows the DJ if you let it. So audio bands, envelopes, and beat-synced clips all move to one clock without a single keyframe.

The master knobs (Output, Speed, BPM) are modulation targets too. Their editors live in the Master modulation rack (the master bar has no room), and a master-brightness LFO can even free-run while the transport is stopped, so the room keeps breathing between sets.

Try it yourself. Full editor, no signup, no time limit: put a track on and map a band to your own strips.