Spectral Bloom

A spectral compressor that gives every frequency band its own compressor. It lifts the quiet detail — partials, breath, noise floor, reverb tails — up toward a moving threshold while reining in the loud peaks, so the sound opens up and blooms. Push it hard and the whole spectrum flattens into something dense, lush, and slightly otherworldly.

How it works

The signal is split into about 512 frequency bins by an overlapping FFT. Each bin runs through its own upward-and-downward compressor against a single shared threshold, and that threshold is adaptive: it sits a fraction below the smoothed peak of each frame — a fraction you set with Floor — so "what counts as quiet" tracks the music's loudness instead of a fixed level. Quiet bins are boosted toward the threshold, loud bins pulled down — raise Amt and the gap closes until the spectrum is nearly level. Left and right run through fully independent pipelines, so a stereo image stays wide. Because it works in frames, there's a short delay (~1024 samples) and the output cold-starts silent and swells in over the first instant — that's expected.

Controls

  • Amt — the compression ratio, from 1:1 (transparent) up to 30:1 (extreme crush). Higher settings flatten the spectrum and bring buried detail forward.
  • Floor — sets the adaptive threshold, the pivot the whole effect rotates around. Down at -40 dB only the very quietest bins bloom, for a clean, selective lift; up toward -6 dB far more of the spectrum is pulled into the boost, for a lusher, noisier wash. The default -20 dB sits naturally in the middle.
  • Rel — how fast each band's compressor recovers, from 2 ms (snappy and dynamic) out to 200 ms, where boosted partials sustain into a smeared, frozen-sounding bloom.
  • Tilt — biases the compression across the spectrum. At center (0 oct) every band is treated equally; turn it positive (toward 3 oct) to compress the highs harder, or negative (toward -3 oct) to weight the lows.
  • Mix — dry/wet blend. At 100% you hear the full effect; back it off to fold the bloom in under the original.

Inputs & outputs

  • inL / inR — stereo audio in; feed a stereo pair, or patch the same mono source to both.
  • Amt / Floor / Rel / Tilt / Mix CV — voltage control over each knob; patch an LFO or envelope to make the bloom breathe, sweep the threshold, or open and close the per-bin recovery.
  • outL / outR — the processed stereo signal.

Tips

  • Feed it reverb returns or sustained pads: the adaptive threshold pulls up tails and overtones for a huge, blooming wash.
  • Modest Amt with a slow LFO into amtcv gives a living, breathing sheen rather than an obvious effect.
  • Tilt toward the highs to add air and shimmer; tilt toward the lows to thicken and glue the bottom end.