Low-Pass Filter (LPF)

Definition

A filter that allows frequencies below a set cutoff point to pass through while attenuating frequencies above it. Used to remove high-frequency harshness, add warmth, or create frequency-sweep effects.

In Simple Terms

Cuts everything above a chosen frequency, removing brightness and letting only the lower, warmer tones through. Useful for taming harsh cymbals, softening synths, or creating the muffled "through a wall" effect.

In Practice

A low-pass filter applied to a synthesizer pad gradually closes during a verse, creating a sense of the sound receding before fully opening in the chorus.

Common Confusion

Sources & Verification

• →
  Bristow-Johnson, R. — Audio EQ Cookbook (biquad filter formulas)
  W3C
  https://www.w3.org/TR/audio-eq-cookbook/
• →
  Smith, J. O. — Introduction to Digital Filters with Audio Applications
  Stanford CCRMA, 2007
  https://ccrma.stanford.edu/~jos/filters/

Last verified: 2026-05-05

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