Filter envelope (env → cutoff)
Concept · First taught in PK1 Snap the filter (Pluck)
A second robot — separate from the volume one — pushing the filter knob up and down for every note you play.
▸What it is
The filter envelope is a second ADSR — separate from the amplitude envelope — that moves the filter cutoff over time. With positive envelope amount, the cutoff opens up at attack and closes down through decay, sustain, release; with negative amount, it opens down and back up. This is the entire mechanism behind classic plucks, snappy basses, and acid lines. A fast decay with high envelope amount gives the "pew" — the filter rushes open and snaps shut on every note. The shape of the envelope and the amount knob together decide how much filter motion every note inherits, even if your finger never touches the cutoff.
▸Questions
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How is the filter envelope different from the amp envelope?
They have the same shape (ADSR) but go to different destinations. Amp envelope controls loudness over time; filter envelope controls cutoff over time.
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What does the envelope amount knob do exactly?
It scales how far the envelope pushes the cutoff. At zero, the envelope is connected but inert; at full positive, every note opens the filter by the maximum range.
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Why is the filter envelope always paired with a filter, never on its own?
The envelope is just a control signal — it needs something to move. The filter is what makes the cutoff motion audible.
▸In the curriculum
First taught
PK1 · Snap the filter — Fast filter decay for the pew. Part of the Pluck track.
Reused in
The same concept comes back in 1 lesson later in the curriculum, in a new context.
▸Related concepts
Concepts that share a lesson with filter envelope (env → cutoff):
Hear what filter envelope (env → cutoff) does to a sound. The PatchPond studio runs in your browser — load a lesson patch and move the knob this concept controls.
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