Vibrato, Wow and Flutter, Morphing Filter

@ghordo ghordo
Fri, 03 Apr 2026 01:53:07 +0000

Left knob — Random Sine Vibrato (±50 cents)

The LFO sweeps from 0.1 Hz (fully CCW, very slow, barely perceptible drift) to 8 Hz (fully CW, classic fast vibrato) with a square-law taper so the slow end has fine resolution. What makes it “random” is that at each zero-crossing the LFO redraws a new amplitude scale in the range [0.4–1.0] using an LCG PRNG. This means cycles are subtly unequal in depth, giving an organic, human-feel pitch waver rather than a mechanical tremolo. Pitch shift is achieved with Hermite-interpolated fractional delay — no pitch artifacts at the interpolation point.

Middle knob — Tape Wow & Flutter

Three layered behaviours that all scale together from the one knob:

Wow — a slow 0.5–3 Hz sine modulates the read position of a tape delay line, causing smooth slow pitch drift like a heavy flywheel tape machine heating up.

Flutter — a faster 6–15 Hz sine with added LCG noise shimmer creates the rapid, irregular speed variation of worn capstan bearings.

Saturation — this widens the stereo image and gives that distinctly grimy cassette-deck character.

Amplitude modulation — flutter is also cross-coupled into a subtle volume warble, linking speed and loudness the way a real tape machine does.

Right knob — Morphing Filter

Fully CCW → Butterworth LP at 600 Hz (dark, muffled)

Noon → Peaking EQ +12 dB at 1 kHz, Q=2 (forward, nasal mid presence)

Fully CW → Butterworth HP at 3 kHz (thin, airy, cuts all the low-end mud

warble filter.endl (166.9 KB)