Filter

Filters are the heart of subtractive synthesis. They work by reducing the amplitude of frequencies in specific ranges. The main filter types are lowpass (removes highs), highpass (removes lows), bandpass (isolates a frequency band), and notch (cuts a narrow band). Key parameters include cutoff frequency (where filtering begins), resonance (boosts frequencies near the cutoff), and slope (how aggressively frequencies are attenuated, measured in dB/octave — 12dB, 24dB, etc.). Different filter models (Moog ladder, MS-20, Oberheim) each have distinct sonic characters. Modulating filter cutoff with envelopes and LFOs creates some of the most iconic sounds in electronic music.