Band is a harmonic bandpass bank for isolating the individual harmonics of a sound. It follows a technique the electronic musician Suzanne Ciani has described: start with a low wave that contains many harmonics, and use a very narrow bandpass filter to pull out one harmonic at a time.
Harmonics are spaced linearly (f0, 2·f0, 3·f0 …), while a normal filter’s cutoff responds exponentially at 1V/oct, so tuning a filter onto one particular harmonic by hand is slow and imprecise. Band instead locks each of its four bands to an integer harmonic of a shared fundamental, so every band is centred exactly on a partial. It can find that fundamental automatically from the incoming audio, or follow a 1V/oct pitch input. The module is 24 HP.
In a patch
How it works
- A shared fundamental
f0is established (auto-detected from the audio, or set by TUNE + V/OCT). - Each of the four bands (A, B, C, D) selects an integer harmonic N; its bandpass center is computed as
N × f0, so it lands exactly on that partial. - WIDTH sets bandwidth as a fraction of f0, giving constant absolute bandwidth: every harmonic isolates equally cleanly (the internal Q auto-scales with N).
- Each band has its own colour (A blue, B green, C orange, D purple) carried into the on-screen spectrum so you can see which band is on which harmonic.
Controls
Per band (×4: A, B, C, D)
| Control | Function |
|---|---|
| Level (top knob) | Output level of that band |
| Harmonic (middle knob) | Which integer harmonic this band isolates (snaps 1-32; 1 = the fundamental) |
| Enable (button + LED) | Switch the band in/out (fast anti-click fade) |
Global (bottom row)
| Control | Function |
|---|---|
| TUNE | Manual fundamental, standard 1V/oct convention (0V = C4) |
| WIDTH | Bandpass bandwidth as a fraction of f0. Narrow settings pass a single harmonic, wider settings let neighbouring harmonics through, and settings above 1 pass clusters |
Inputs
| Input | Function |
|---|---|
| IN | Audio input: the source whose harmonics you are isolating |
| V/OCT | Fundamental pitch, 1V/oct (matches a standard oscillator; used in manual mode) |
| SHIFT | Global continuous harmonic shift; slides all bands between harmonics at once (1V = 1 harmonic) for scanning across the series |
| W-CV | Width modulation |
| Per band: Level CV | Modulates that band’s level (10V → +full) |
| Per band: Harmonic CV | Continuously shifts that band’s harmonic (1V = 1 harmonic) |
| Per band: Enable gate | Gate ≥1V forces the band on (overrides its button when patched) |
Outputs
| Output | Function |
|---|---|
| MIX | Sum of all enabled bands (each × its level) |
| POLY | Each band on its own polyphonic channel (A=1, B=2, C=3, D=4). Spatialize or process harmonics separately |
The display
The display is a spectrum analyzer (FFT) of the incoming audio, drawn on a harmonic axis (frequency ÷ f0) so that the spectral peaks line up with the harmonic gridlines. Each band is drawn as a coloured bell-shaped curve centred on its harmonic, with its height showing the band’s level, and labelled with its letter and harmonic number (e.g. A5 = band A on harmonic 5). The readout at the bottom-left shows the current f0 in Hz, with AUTO shown when the pitch is being auto-detected.
Auto-follow vs. manual
- Auto-follow (default, context menu): Band detects the source’s fundamental directly from the audio (FFT autocorrelation) and locks the harmonic grid to it. Feed it a wave that contains many harmonics and the bands move onto those harmonics with no tuning. When a melody plays into IN, the whole bank follows its pitch. (V/OCT and TUNE are ignored while auto-follow is locked.)
- Manual: turn auto-follow off and set the fundamental with TUNE + V/OCT. Because Band uses the standard 1V/oct reference, patching the same pitch CV into both your oscillator and Band’s V/OCT keeps the harmonics aligned exactly at every note. This is the most precise option, especially for high harmonics.
Context menu
- Follow input pitch (auto-lock harmonics): toggle auto-detection (default on).
- Filter slope: 4-pole (steep, default) or 2-pole (gentler).
Patch ideas
Ciani-style harmonic isolation. Feed a low saw or pulse (~30-110 Hz) into IN. Leave auto-follow on. Turn WIDTH right down, then set A/B/C/D to different harmonics; each rings out a single partial. Bring WIDTH up slightly to let some of the neighbouring harmonics through.
Additive re-voicing. Isolate harmonics 1, 2, 3, 5 across the four bands and ride their Levels (or modulate with LFOs/envelopes) to re-balance the timbre of any source in real time.
Spatial harmonics. Take the POLY output into four VCAs/panners (or a poly VCA) and place each harmonic in its own position in the stereo field.
Harmonic sequencing. Sequence the per-band Harmonic CVs (1V/harmonic) or the global SHIFT to step the bands up and down the harmonic series in time with your patch.
Vocoder-like movement. Modulate WIDTH and SHIFT slowly with LFOs while the source plays. The bands slide across the partials and widen and narrow as they go, which gives a moving, formant-like tone.
In the synthesis guide
- Synth Filters Explained: Cutoff, Resonance, Slope
A filter reduces the harmonics above or below a chosen frequency. Cutoff sets that frequency, resonance boosts the harmonics around it, and slope sets how steeply the level falls beyond it.
