Subtractive synthesis removes frequencies from a rich source using resonant low-pass or high-pass filters

Subtractive synthesis starts with a harmonically rich source (saw, square, noise) and uses filters to remove frequency ranges. A low-pass filter (:lpf) passes low frequencies and cuts highs; its cutoff: sets the transition point. A high-pass filter (:hpf) does the opposite. Modulating cutoff: over time creates movement — the characteristic sweep of subtractive synthesis. Lower cutoff values sound warmer/darker; higher values brighter/buzzier.

Examples

with_fx :lpf, cutoff: 70 do synth :saw, note: :e2, release: 4 end

Assessment

Apply :lpf with cutoff sweeping from 40 to 120 over 4 beats. Describe how the timbre changes. Explain why a low-pass filter is the essential starting point for subtractive synthesis.