Pinch

A two-stage S-curve shaper centered on 0.5, with optional opposite curvature on the right lane.

What it does #

Pinch redistributes a nominally unipolar signal around its midpoint. It keeps 0, 0.5, and 1 anchored while changing how quickly values approach or leave the middle, producing a symmetric S-shaped transfer rather than Bend's sign-preserving magnitude curve.

Controls and ports #

Control	Label	Official description
amount	Amount	S-curve factor, where '0 %' results in no change, positive values impose a logarithmic-type S-curve, and negative values impose an exponential one

Practical uses #

• Reshape unipolar envelopes, fades, crossfade positions, or phase-derived control curves while preserving their endpoints and midpoint.
• Alter swing or movement character when a 0-to-1 ramp drives a later lookup or routing module.
• Enable Stereo-ize for opposing left/right curvature from one shared input.

Things to know #

• The recovered formula is centered on 0.5 and is therefore naturally suited to unipolar signals.
• The endpoints 0 and 1 and the midpoint 0.5 are fixed for the nominal range.
• The same quadratic bend is applied twice to distance from the midpoint.
• Bipolar and out-of-range inputs can leave the intuitive S-curve region and need direct measurement.

Technical details #

A high-confidence Nitro implementation candidate supports the technical summary, but the visible-module mapping remains inferred.

The exact grid/level/grid_level_pinch body sets u=2*in-1, a=abs(u), and c=amount or alternating ±Amount under Stereo-ize. It applies F(z,c)=z*(1+c*(1-z)) twice, then reconstructs out=0.5*(copySign(F(F(a,c),c),u)+1). This mathematically fixes inputs 0, 0.5, and 1 and uses no transcendental logarithm or exponential.

Nitro port	Type
in	InputAudioPortType
b	InputAudioPortType
stereoize	InputValuePortType
out	OutputAudioPortType

Open questions #

• Measure transfer points across both Amount polarities and confirm the visible range.
• Test bipolar and out-of-range inputs, Stereo-ize lane order, modulation smoothing, and audio-rate shaping.
• Verify non-finite values, exact endpoints, and whether the UI clamps Amount before Nitro.

Version and sources #

Checked against Bitwig Studio 6.0.6. This page combines Bitwig's module metadata, the existing Grid course and guides, and Nitro analysis where the mapping is strong enough to support a technical statement.

Related material #

• Grid Modules course reference

Return to Bitwig Grid Modules or the Grid Modules course lesson.