F_GRAVZ

GRAVZ – Stereo Gravity Filter

GRAVZ is a stereo filter and spatial shaping module built for real stereo work. Instead of treating the left and right channels as two independent filters, GRAVZ is designed around the idea that a stereo signal consists of a stable center (MID) and a spatial component (SIDE). The MID acts as an anchor for focus, punch and mono compatibility, while the SIDE carries width, movement and air. GRAVZ allows you to shape these two components in a controlled, musical way, making it possible to add depth and stereo interest without collapsing the mix or introducing unstable phase behavior.

Signal Flow

The incoming stereo signal is converted internally to MID and SIDE. A shared cutoff foundation is established first, defining whether sound energy is present at all. This shared cutoff serves as the absolute gate for both MID and SIDE, ensuring predictable filter behavior. From this foundation, the SIDE frequency response can be shifted relative to the MID using the GRAV control. Both MID and SIDE pass through state-variable filters that can continuously morph between low-pass, band-pass and high-pass behavior using the WARP control. After filtering, a tilt stage shapes the spectral balance around a pivot frequency, after which the signal is recombined back into left and right outputs. In SAFE mode, an additional stabilization stage continuously monitors SIDE energy and gently reins it in when settings become extreme, preserving clarity and mono compatibility.

Inputs and Outputs

At the top of the module are the stereo audio inputs labeled L and R. Next to them is the ENV input, which accepts a standard unipolar envelope signal in the range of 0–5V, typically from an ADSR. At the bottom of the module are the stereo outputs labeled L and R.

Cutoff (CUT)

The CUT knob sets the base cutoff position of the filter. The cutoff can be fully closed, allowing the low-pass response to shut completely. This cutoff position determines whether MID and SIDE carry any energy at all and forms the foundation for all further modulation, including envelope and CV modulation. If the cutoff is fully closed and no envelope is applied, the module outputs silence unless the LEAK function is enabled.

Resonance (RESO)

The RESO knob controls the resonance (Q) of the filter. Low values produce smooth, gentle filtering, while higher values emphasize frequencies around the cutoff and allow the filter to ring. Resonance is applied consistently to both MID and SIDE paths, maintaining tonal coherence across the stereo field.

Envelope Amount (ENV)

The ENV knob controls how strongly the envelope input modulates the cutoff. The envelope signal itself is unipolar (0–5V), while the ENV knob is bipolar, ranging from –1 to +1. Positive values cause the envelope to push the cutoff upwards, while negative values invert the behavior and pull the cutoff downwards. The envelope operates in the cutoff control domain rather than directly in Hertz, allowing it to open the filter even when the cutoff knob is fully closed. This makes the envelope equally effective for low-pass, band-pass and high-pass operation.

Envelope and Stereo Interaction

The envelope always defines a single, coherent filter movement, ensuring tight timing and stable transients. In MID/SIDE operation, the envelope influence is subtly redistributed between MID and SIDE based on the FOCUS control. As FOCUS moves towards the SIDE, the envelope exerts slightly more influence on the SIDE than on the MID, allowing the stereo image to breathe and expand without introducing timing offsets or image instability.

Warp (WARP)

The WARP control continuously morphs the filter response from low-pass through band-pass to high-pass. This morphing is smooth and free of switching artifacts. In MID/SIDE operation, the SIDE path is allowed a slightly more pronounced warp response, adding air and motion while keeping the MID solid and centered.

Focus (FOCUS)

FOCUS determines how strongly processing affects the SIDE relative to the MID. Turning FOCUS towards the left emphasizes the MID, keeping the stereo image tight and centered. Turning it towards the right increases SIDE influence, adding width, movement and spatial detail. FOCUS also influences how envelope modulation is distributed between MID and SIDE, reinforcing the sense of stereo gravity.

Gravity (GRAV)

GRAV shifts the cutoff frequency of the SIDE relative to the MID in musical octave steps. Positive values make the SIDE brighter and more open, while negative values darken and tighten the stereo field. Because this operates in the MID/SIDE domain rather than directly on left and right channels, it creates width without introducing phase problems.

Tilt (TILT)

The TILT control applies a spectral tilt around the pivot frequency. In MID/SIDE mode, the MID is tilted gently while the SIDE is tilted in the opposite direction with slightly more emphasis. This allows you to add clarity, shimmer or weight to the stereo image without relying on traditional equalizers.

Pivot (PIVOT)

PIVOT sets the frequency around which the tilt operates. Lower pivot values affect the low and low-mid balance, while higher values focus the tilt on presence and air frequencies. The pivot frequency is shared by both MID and SIDE tilt stages.

Drive (DRIVE)

DRIVE adds gentle saturation before the filtering stage. This can add density and character, especially when combined with resonance or envelope modulation. The drive stage is applied equally to both channels to preserve stereo balance.

Mix (MIX)

MIX controls the balance between the dry input signal and the processed signal. This allows GRAVZ to be used subtly as a stereo stabilizer and tone shaper, or aggressively as a sound-design tool.

Leak (LEAK)

The LEAK switch controls whether the SIDE signal is allowed to bypass the cutoff gate when the filter is fully closed. With LEAK disabled, the module behaves strictly: if the cutoff is closed and no envelope is applied, both MID and SIDE are silent. With LEAK enabled, a controlled amount of raw SIDE signal is allowed to bleed through when the cutoff is closed, after which it is still shaped by GRAV, TILT and PIVOT. This creates airy, spatial textures and subtle stereo presence even when the filter itself is shut.

Modes

GRAVZ offers three operating modes. Mode 1 (L/R) processes the signal as traditional left and right channels with linked stereo behavior. Mode 2 (M/S) activates the full gravity concept, processing MID and SIDE separately for maximum spatial control and musical coherence. Mode 3 (SAFE) builds on M/S mode by adding adaptive SIDE stabilization that continuously keeps the stereo image controlled and mix-ready, even with extreme settings.

Modulation Inputs

The modulation inputs are arranged in three rows. The first row provides CV inputs for CUT and RESO. The second row provides CV inputs for WARP, FOCUS and GRAV. The third row provides CV inputs for TILT, DRIVE and MIX. All modulation inputs are additive and are applied before smoothing, allowing expressive and dynamic modulation without zipper noise.

Typical Use Cases

GRAVZ is highly effective on pads and sustained synths, where it can add width and motion while keeping the center stable. On reverb returns, it excels at shaping space, allowing you to brighten, widen or thin out the stereo field without muddying the mix. On drums and percussion, GRAVZ can be used to control stereo low end with high-pass envelopes, tighten overheads, or add controlled air using the LEAK function. For sound design and transitions, extreme GRAV, TILT and WARP settings combined with LEAK enable collapsing, expanding and breathing stereo effects that remain controllable and mono-safe.

Conceptual Summary

GRAVZ is not just a filter, but a stereo control instrument. By separating stability in the MID from space in the SIDE and giving you musical control over how energy is gated, distributed and shaped, GRAVZ provides a way to design stereo sound that feels intuitive, reliable and indispensable once integrated into a workflow.

Why it is called GRAVZ

The name GRAVZ comes from the idea of gravity as a shaping force rather than an effect. In a stereo signal, not all sound carries the same perceptual weight: the center naturally feels heavier, more grounded and more stable, while the sides feel lighter, wider and more mobile. GRAVZ is designed around this imbalance. The MID acts as the gravitational center, anchoring the sound, while the SIDE is allowed to orbit around it. Controls like FOCUS and GRAV do not simply make the signal wider or narrower; they change how strongly the sound is pulled toward the center or allowed to drift outward. Even when the filter is pushed into motion, gravity remains present: energy must exist before space can be shaped, and movement always happens relative to a stable reference. GRAVZ is therefore not about flattening stereo or exaggerating width, but about sculpting how sound settles, spreads and moves under an imagined gravitational field.

1. Center Anchor

CUT 450 Hz, RESO 2.0, ENV 0.0, WARP 0.00, FOCUS –0.45, GRAV 0.00, TILT 0.00, PIVOT 1200 Hz, DRIVE 0.00, MIX 1.00, MODE 1, LEAK 0. A neutral, mix-ready preset that lightly smooths the sound while keeping the MID firmly anchored and the stereo image stable.

2. Wide Air Lift

CUT 6500 Hz, RESO 1.6, ENV 0.0, WARP 0.35, FOCUS +0.65, GRAV +0.40, TILT +0.45, PIVOT 4200 Hz, DRIVE 0.00, MIX 1.00, MODE 1, LEAK 0. Opens the stereo field with airy highs while the center remains controlled and mono-safe.

3. Mono-Safe Low Cut

CUT 180 Hz, RESO 0.5, ENV 0.0, WARP 0.95, FOCUS +0.55, GRAV +0.25, TILT –0.20, PIVOT 300 Hz, DRIVE 0.00, MIX 1.00, MODE 2, LEAK 0. Cleans up stereo low end without collapsing width, ideal for drum buses, loops and overheads.

4. Classic LP Pluck

CUT 90 Hz, RESO 8.0, ENV +0.75, WARP 0.00, FOCUS –0.25, GRAV 0.00, TILT 0.00, PIVOT 1000 Hz, DRIVE 0.00, MIX 1.00, MODE 1, LEAK 0. Feed a short ADSR into ENV for tight, punchy low-pass plucks with stable stereo behavior.

5. HP Punch Control

CUT 900 Hz, RESO 0.5, ENV –0.60, WARP 1.00, FOCUS +0.35, GRAV +0.30, TILT 0.00, PIVOT 350 Hz, DRIVE 0.00, MIX 1.00, MODE 1, LEAK 0. Envelope-driven high-pass shaping that tightens transients and controls low-end punch.

6. Breathing Space

CUT 1800 Hz, RESO 0.8, ENV 0.0, WARP 0.30, FOCUS +0.60, GRAV +0.35, TILT +0.30, PIVOT 2500 Hz, DRIVE 0.00, MIX 1.00, MODE 1, LEAK 0. Slowly modulate FOCUS with a slow LFO for gentle, breathing stereo motion.

7. Side Shimmer Motion

CUT 9000 Hz, RESO 3.5, ENV 0.0, WARP 0.65, FOCUS +0.75, GRAV +0.50, TILT +0.65, PIVOT 4800 Hz, DRIVE 0.00, MIX 1.00, MODE 2, LEAK 0. Produces animated stereo highs while keeping the MID clean and controlled.

8. Leak Air Ghost

CUT 2 Hz, RESO 0.5, ENV 0.0, WARP 0.40, FOCUS +0.80, GRAV +0.45, TILT +0.55, PIVOT 3500 Hz, DRIVE 0.00, MIX 1.00, MODE 1, LEAK 1. With the filter closed, airy SIDE content bleeds through and is shaped spectrally for atmospheric textures.

9. Gravity Collapse

CUT 220 Hz, RESO 14.0, ENV 0.0, WARP 0.80, FOCUS +1.00, GRAV –0.70, TILT –0.75, PIVOT 500 Hz, DRIVE 0.40, MIX 1.00, MODE 2, LEAK 1. Extreme stereo sculpting where the center stays anchored while the sides implode and expand.

10. Mix Glue Control

CUT 480 Hz, RESO 1.2, ENV 0.0, WARP 0.20, FOCUS –0.20, GRAV 0.00, TILT +0.10, PIVOT 1500 Hz, DRIVE 0.00, MIX 0.65, MODE 1, LEAK 0. Subtle stereo cohesion and smoothing that quietly glues a mix or stem together.