Interval
Which pitch the toe-down position aims for (octave up/down, dive, harmony zones).
- Turn up Toward higher pitch intervals (e.g. octave up).
- Turn down Toward lower / dive-bomb style intervals.
Pedals / Pitch shifter
Bend Box
Pitch shifter · play-tested
seth — fish
seth@ninevolt:~$
Knobs
In the TUI each knob runs from low (left / 0%) to high (right / 100%). Start near noon, then nudge while you play.
Mix
Dry guitar versus pitched signal.
- Turn up More pitch-shifted sound.
- Turn down More dry guitar underneath.
Glide
How smoothly pitch moves when you change expression / interval.
- Turn up Slower, swoopier bends.
- Turn down Snappier pitch changes.
Inspired by
DigiTech Whammy (1991 onward) — preset knob, expression treadle, and footswitch. Whammy bends (octave up/down, dive bomb), Harmony presets (treadle sweeps between two pitches), and Detune. Bend Box maps the preset knob to Interval and the treadle to MIDI expression (not an on-screen knob).
Signal path
| Step | What it does |
|---|---|
| High-pass when pitching down | ~72 Hz HPF on octave-/fifth-down paths to reduce sub rumble. |
| Delay line write | Conditioned sample stored in a sample-rate-sized ring buffer. |
| Expression treadle | Interval picks the toe-down pitch; MIDI expression (0 = heel / unity, 1 = toe) interpolates in 12-TET log space. |
| Glide smooths ratio | Glide slews current_ratio toward the treadle target (8 ms–830 ms). |
| Variable-speed read + crossfade reset | Read head advances at current_ratio; equal-power crossfade on buffer reset (~22 ms). |
| Wet anti-alias LP | Low-pass when pitching up to tame aliasing. |
| Soft tanh | Light saturation on the wet path. |
| Wet/dry Mix | Mix blends dry input and shifted signal. |
| Output | Clamped mono sample. |
How we modeled it
Interval = preset knob. Expression = treadle via MIDI (starts at toe-down until you move the pedal). Glide + Mix are Ninevolt extras for dive-bomb shaping and dry blend.
Simplifications
- Heel is always unity; harmony modes that sweep between two shifted intervals (e.g. 4th→5th) are not modeled yet - Monophonic — chords show artifacts (Classic-mode Whammy) - No Detune mode or Classic/Chords switch