The kākāpō digs a bowl in the earth and booms all night — a sub-100 Hz call that carries for kilometres, the loudest low end in the bird world. This one listens to your bass, finds the note, and booms underneath it: a pure, phase-locked sub oscillator that follows your track's own audio. No MIDI, no second synth, no re-writing the bassline. Your growl keeps its mids; Kakapo supplies the floor.
Every processed bass trades low end for character — the growl gets the mids, the reese gets the movement, and the fundamental gets eaten alive. The usual fix is layering a sine synth under it, which means writing the MIDI twice, tuning the layer forever, and praying the two stay in phase. Kakapo skips all of it: insert it on the bass, and it generates the clean sub from the audio itself.
Kakapo tracks the fundamental of whatever is playing, snaps it to the nearest note, and runs a phase-continuous sine underneath — riding your input's own envelope, gated by your input's own level, and phase-locked to your input's own cycle so the layered low end sums instead of beating. Turn one knob and the floor is back.
Nothing else in our catalog creates low end — Grosbeak fattens what is there, Kea and Cassowary protect the sub while they work the mids, Crossbill folds. Kakapo is the missing foundation tool: the plugin you insert before any of them, so there is a foundation to protect. It generates its sub from tracked pitch — not by octave-dividing the input — so the sub is always a clean oscillator at a real note, never a colored copy of your source's wobble.
A sub generator lives or dies on its tracker: one octave error and the drop falls apart. Kakapo's detector is a ground-up autocorrelation engine — it correlates the signal against itself across every candidate period and reads the pitch from where the waveform genuinely repeats, with a built-in measure of how confident that answer is. The verification suite drives it with sines, sawtooths, noise bursts, and 808 slides — eighteen gates, all green, numbers below.
A normalized square-difference engine in the McLeod family — the method proper tuners use — with parabolic refinement of the winning period. Accuracy on reference bass tones measures within a tenth of a cent, and the first-major-peak rule resists octave flips structurally; a flip that still tries needs five agreeing readings before it is even considered.
Every reading carries a clarity score — how periodic the window actually was. Noise scores low and simply produces no reading at all, so there is nothing to chase: through a full-level broadband noise burst the held note drifts by six cents, measured. No thresholds to tune, no heuristics bolted on — it falls out of the math.
Note changes confirm by consecutive agreeing readings — each within earshot of the last, so an 808 slide keeps confirming as it moves instead of stalling on a frozen reference. A 300 ms octave slide tracks continuously through its whole length and settles dead on target.
When the input drops away — silence, a gap, a drum fill — the pitch holds exactly where it was and only the level gates out. No decaying pitch slides, no reset to a default note. The next note picks up from a sane place, and a kick-only passage can keep booming the last note on purpose.
Raw tracked pitch is honest but wobbly — a detuned reese is genuinely fifteen cents flat. Between the tracker and the oscillator sit four controls that turn what the bass is into what the sub should be.
Chromatic quantize with hysteresis: at 100 the sub lands exactly on the nearest semitone and vibrato cannot make it flutter across a note boundary. At 0 it follows every bend verbatim — the 808-slide setting. Defaults to 100, because basslines live on notes.
Portamento between targets, measured in the musical domain so an octave takes as long as a semitone is smooth. Short keeps riffs tight; long turns note changes into a synth-bass slide under the whole pattern.
Shifts the generated sub against the tracked note: −2, −1, 0 or +1 octaves. A midrange stab at G2 becomes a G1 foundation at −1; a bass already living at 40 Hz gets reinforced in place at 0.
The differentiator. LOCK phase-locks the oscillator to your input's actual cycle, and PHASE dials in the alignment — so when you layer the sub under your kept low end, the two sum instead of slowly beating against each other. Verified to a tenth of a degree.
SHAPE morphs the pure sine toward a rounded square, adding only odd harmonics — the third and fifth that let a sub read on laptop speakers and earbuds. Even harmonics would smear the pitch an octave up, so the morph is built symmetric: measured even-harmonic content is 146 dB below the fundamental, which is to say none.
At 100, the sub tracks your input's dynamics one to one — 6 dB louder in, 6 dB louder sub, measured to within a twentieth of a dB. At 0, the sub holds a flat level for as long as the gate is open: compressed-bass behaviour without a compressor in sight.
SENSE sets how much input it takes to open the sub, with 6 dB of hysteresis and a minimum-open hold so a level parked on the threshold cannot stutter the low end. Attack and release shape how the sub arrives and leaves — from drum-tight gating to long half-time tails.
The generated sub is one oscillator sent identically to both channels — not a stereo signal folded down, but mono at the source, the way club systems and vinyl want the bottom octave. Verified in the suite: soloed sub side energy is zero to numerical precision.
The dry signal is split at X-OVER with a Linkwitz-Riley pair whose two halves are phase-matched by design — at full DRY LO with the sub off, Kakapo measures flat to a thousandth of a dB from 20 Hz to 18 kHz. Insert it, and until you ask for something, nothing happens.
DRY LO is your original low end's fader. At 100 the sub layers underneath everything you had — the default, because a generator should do no harm on insert. At 0 the crossover removes your dry lows entirely and Kakapo's oscillator becomes the foundation: a clean, tuned, phase-stable replacement for a wobbling original.
LO MONO folds the kept dry lows below the crossover to mono, so a wide reese can keep its stereo mids while its bottom octave locks to the center with the generated sub. Off by default — it only touches your signal when you ask.
SUB SOLO auditions the generated lane alone — tuning SHAPE, checking the octave, or bouncing the sub as its own stem. The crossfade is click-free, and what you hear soloed is bit-for-bit what gets summed.
TRACK decides when and what the tracker believes; the pitch bar decides what note the sub plays; SUB decides how it sounds; BLEND decides how it meets your signal. The defaults are the calling card: insert it on a bass and the floor appears.
How much input opens the gate — mapped from −25 to −65 dBFS with 6 dB of hysteresis and a 60 ms minimum-open hold.
How fast the sub's level follows the input upward. Short for drum-tight arrival, long for swells.
How the sub lets go when the input stops. Long settings turn staccato stabs into a sustained floor.
Chromatic quantize with anti-flutter hysteresis. 100 = always in tune; 0 = follow every bend and slide verbatim.
Portamento between pitch targets, constant in musical terms across the range. The note-change smoother.
Shifts the generated sub against the tracked note. −1 turns a midrange riff into a proper sub line.
Phase-locks the oscillator to the input's cycle so layered lows sum instead of beating. Releases automatically when Snap pulls the pitch away.
The lock's alignment target. Tune it while watching the scope — or by ear — for the fattest sum with your kept lows.
The generated lane's level, with headroom above unity for when the sub is the whole point.
Sine to rounded square. Adds odd harmonics only — small-speaker presence without shifting the perceived octave.
How much the sub rides your input's dynamics. 0 holds a flat −12 dBFS while the gate is open.
Where your dry signal splits. Everything above passes untouched; everything below is DRY LO's territory.
Your original lows' fader. 100 layers the sub under them; 0 hands the low end to Kakapo entirely.
Folds the kept dry lows to mono below the crossover. The generated sub is already mono by construction.
Output trim after the sum, for level-matched comparisons against bypass.
Auditions the generated sub alone, click-free. What you hear is exactly what gets added.
A pitch tracker has real physics, and burying them would only cost you time later. These are the four worth knowing before you buy.
Kakapo tracks one fundamental. Basslines, stabs, leads, 808s — yes. Chords, full mixes, or two basses at once give it two answers to a one-answer question; it will pick the strongest and stick to it, which may not be the one you meant. Put it on the bass channel, not the master.
The detector needs a few cycles of a note to trust it — at 50 Hz, a cycle is 20 ms, so a new note settles in tens of milliseconds. The dry path is untouched zero-latency; only the generated sub's arrival is shaped by that settle plus your ATTACK and GLIDE. Sustained bass: perfect. Chromatic 32nd-note runs at 30 Hz: physics says no.
The tracker listens below 500 Hz by design — it is a bass tool, and ignoring the upper spectrum is what makes it hard to fool. A part whose fundamental lives above 500 Hz (pads, plucked melodies up high) is outside the contract.
1.0 tracks audio only. A MIDI side-input — play the notes in and skip the tracker entirely — is the planned 1.x headline, and the engine was built with the seam in place. Until then, SNAP at 100 gets you the always-in-tune result MIDI would.