Pitch Shift

A three-grain stereo delay-line pitch transposer with keytracking, adaptive grain timing, crossfades, and phase/FM input.

What it does #

The current editorial summary is: A three-grain stereo delay-line pitch transposer with keytracking, adaptive grain timing, crossfades, and phase/FM input.

Pitch Shift continuously records audio into stereo delay lines and reads it through three overlapping cosine-windowed grains. Moving the read positions relative to the write head changes pitch, while Grain Rate, Fade, Adaptive mode, detune, keytracking, and phase/FM input expose the reconstruction process for both clean-ish transposition and deliberate artifacts.

Controls and ports #

Control	Label	Official description
shift	Shift	Semitone (half-step) shift applied to the incoming audio signal
keytrack	Keytrack	Pre-cord adding device's pitch signals (via incoming notes) to the pitch shift amount
phase_fm_in	Phase Fm In	Phase / FM modulation of the shifting oscillator
pitch_in	Pitch In	Control input added to the pitch shift amount
grain_rate	Grain Rate	Windowing rate used (when Grain Rate In is not connected)
grain_rate_mult	Grain Rate Mult	Attenuator ratio for the Grain Rate In signal. Low settings mean slower rates, and high settings mean faster rates.
grain_rate_in	Grain Rate In	Signal control of the grain rate (instead of the Grain Rate parameter)
adaptive	Adaptive	Adjusts grain rate to correspond with pitch shift amount
fade	Fade	Transition time between successive frames
fm	Fm	When enabled, does linear frequency modulation (instead of phase modulation) with the second in port. Note that FM is only possible when pitch shifting is occurring.

Practical uses #

• Transpose by musical intervals and enable Adaptive Grain Rate as a practical starting point for stable material.
• Lower Grain Rate or alter Fade to turn the processor into a rhythmic grain delay, resonator, or metallic texture generator.
• Feed audio into Phase/FM In to impose sidebands and complex pitch movement on the grains.

Things to know #

• The shifter always relies on buffered history and overlapping windows, so latency and transient smearing are part of the design.
• Three grains are phase-offset by one third of a cycle and summed to reduce amplitude gaps.
• Adaptive mode changes Grain Rate as a function of pitch ratio rather than leaving it fixed.
• FM and PM use different scaling and phase-update paths; FM is enabled only when actual pitch shifting is active at the visible level.
• Very low or high Grain Rate and short Fade values trade smoother continuity for stronger rhythmic or metallic artifacts.

Technical details #

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

The exact mod_fx/pitch_shifter_module uses independent left/right delay lines and NUM_SHIFTERS = 3 with phase offsets 0, 1/3, and 2/3. Requested pitch becomes 2^((key-60)/12) with a ±120-semitone internal clamp plus stereo detune. Grain Rate is optionally adapted by ((ratio-1)*0.25+1), then clamped to 1.8–1000 Hz. Each grain reads a linearly interpolated position through a cosine window; parameter changes crossfade between two grain states. PM offsets read positions, FM changes phase advance, and the final wet signal is equal-power mixed with the input.

Nitro port	Type
pitchValue	InputAudioPortType
pitchOffset	InputAudioPortType
numerator	InputValuePortType
denominator	InputValuePortType
phaseIn	InputAudioPortType
phaseMod	InputAudioPortType
stereo	InputValuePortType
detune	InputAudioPortType
in	InputAudioPortType
gain	InputAudioPortType
mix	InputAudioPortType
fm_pm_mod	InputValuePortType
grain_fade	InputAudioPortType
adaptive_grain_rate	InputValuePortType
grain_rate	InputAudioPortType
out	OutputAudioPortType

Open questions #

• Measure actual latency, unity-shift transparency, transient smearing, and artifact spectra over Grain Rate and Fade.
• Confirm numerator/denominator ratio use, visible keytracking mapping, stereo detune range, and the ±120-semitone clamp at the wrapper.
• Test PM/FM scaling, adaptive-rate transitions, equal-power Mix law, reset behavior, and parameter-change crossfade timing.

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 #

• Pitch Shift in Bitwig 5.3
• Bitwig Pitch-Shifter Device - Grain-Based Pitch Shifting

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