Spectral Smear

A stereo spectral blur. It dissolves the sharp edges of a sound by averaging neighbouring frequencies together and scattering their phases — turning tones into breathy, noise-shaped clouds that still trace the original envelope. Push it hard and a voice, pad, or drum loop loses its pitch identity and becomes a wash of coloured air.

How it works

The signal is analysed in overlapping FFT frames. For each frame, every frequency bin's level is replaced with the average level across a band of its neighbours — a wider band means a blurrier spectrum, up to the ceiling you set with Reach — and the phases are scrambled by a separate amount you dial in with Scatter. A makeup gain restores energy lost to the averaging, so smearing a pitched sound never collapses into silence; it spreads out instead. Because the blur works on the spectrum rather than in time, the result keeps following the input's loudness while shedding its tonal detail. The two channels share the same magnitudes but get independently scattered phases, so the cloud widens into stereo as you open it up.

Controls

  • Width — the heart of the effect: how far each frequency bleeds into its neighbours. At 0% the sound passes through untouched; toward 100% the spectrum blurs across a wide band and phases fully randomize into noise.
  • Tilt — biases the smear across the spectrum, up to ±3 octaves. At centre (0 oct) the blur is even; turn positive to smear the highs harder while keeping lows tight, negative to do the reverse.
  • Scatter — how hard the phases are scrambled, set apart from the blur itself. At 0% the phases stay intact for a pure magnitude blur — a soft tonal melt that still holds a sense of pitch and transient; toward 100% (the default) phases fully randomize into a diffuse, reverb-like wash, which is also what widens the cloud into stereo.
  • Reach — the top frequency the smear climbs to. Pull it down toward 1.5 kHz to confine the blur to the low end while cymbals and air stay crisp; open it up toward 24 kHz to let the whole spectrum melt into the cloud. It sits around 6 kHz by default.
  • Mix — dry/wet blend. 100% is fully smeared; back it off to keep the original sound present underneath the cloud.

Inputs & outputs

  • In L / In R — the stereo signal to smear. For a mono source, patch it to both jacks to spread it into the wide, decorrelated cloud; feed just one side and only that channel sounds.
  • Width / Tilt / Scatter / Reach / Mix CV — voltage control over each knob; patch an LFO or envelope to make the smear breathe, tilt the bias, dial the phase scatter, sweep its reach, or fade the wet cloud in and out (10 V covers the full range, added to or subtracted from the knob setting).
  • Out L / Out R — the processed stereo output.

Tips

  • There's about a frame of latency, and the output cold-starts silent and swells in over the first moments — expect a brief fade-up when sound first arrives.
  • For a slowly breathing texture, send a slow LFO into Width CV and leave Mix wide open.
  • Use a negative Tilt to blur bass into a rumble while leaving cymbals and transients crisp — or flip it to smear only the air on top.