Ancora — Manual

The stereo field has been central to audio production since the earliest days of multi-channel recording. When Alan Blumlein first demonstrated his stereophonic recording system in the 1930s, he revealed a new dimension in sound reproduction — the ability to locate sound sources in space, to create width and depth, to craft an immersive listening experience. Yet this advance also introduced new challenges, particularly when that carefully crafted stereo image must translate to mono playback.

Mono compatibility is not a relic of the past. Radio broadcasts, mobile device speakers, club sound systems, voice assistants, automotive systems — all commonly sum stereo signals to mono. When poorly managed phase relationships and extreme panning decisions encounter this summation, the results can be devastating: elements disappearing entirely, dramatic frequency cancellations, a mix that loses its fundamental balance and impact.

Beyond mono playback, stereo correlation plays a critical role in vinyl cutting, where excessive stereo width can cause physical cutting problems and stylus tracking issues. The cutting lathe must translate lateral and vertical groove modulations, and when left and right channels contain vastly different information — particularly at low frequencies — the mechanical limits of the medium can be exceeded. Mastering engineers have long managed correlation to ensure reliable vinyl pressings that play back cleanly without distortion or skipping.

Traditional approaches to ensuring mono compatibility often involve compromises. Narrow the stereo image too much and you sacrifice the space and dimension that makes modern mixes engaging. Leave the image too wide and you risk phase cancellations that can hollow out critical elements when summed to mono. Mid/Side processing offers powerful control, but requires careful management to avoid creating new problems while solving existing ones.

The concept of stereo correlation provides a more sophisticated framework for understanding these relationships. Perfect correlation (1.0) indicates that left and right channels are identical — effectively mono. Zero correlation means the channels are completely independent, maximizing stereo width but also creating the most potential for phase issues. Negative correlation represents out-of-phase relationships that can cause severe cancellations in mono. Unlike traditional correlation meters that only measure waveform similarity, Ancora's measurement is based on spectral Mid/Side balance — capturing not just phase relationships but also panning asymmetries that affect mono translation and vinyl cutting.

But correlation is not a single number — it varies across the frequency spectrum. A vocal might be perfectly centered (high correlation) while cymbals spread wide (lower correlation). Bass frequencies often benefit from tighter correlation to maintain power in mono, while high frequencies can afford more independence for a sense of air and space. Managing these frequency-dependent relationships is the key to achieving both an engaging stereo image and solid mono translation.

The goal is not to eliminate stereo width, nor to force everything into perfect mono compatibility at the expense of dimension. Rather, it's to intelligently manage the stereo field — preserving width where it serves the music while controlling problematic panning and phase relationships that compromise mono translation. Whether working in Left/Right mode to reduce excessive panning differences or Mid/Side mode to control the side channel directly, both approaches improve stereo correlation by bringing the left and right channels into closer agreement where needed. This requires tools that understand the frequency-dependent nature of stereo imaging and can apply precise, musical control where needed.

Ancora (which draws its name from the Latin word for 'anchor') is a stereo image correction processor that intelligently manages stereo width and improves mono compatibility through frequency-dependent panning & width correction. Operating without fixed crossovers, Ancora analyzes stereo content in real-time and applies precise corrections based on three customizable curves: Depth, Timing, and Target.

The processor offers two complementary processing modes. In L/R mode, Ancora analyzes the panning difference between left and right channels, reducing excessive panning that exceeds the Target threshold. This brings overly wide elements closer to center while maintaining the overall stereo field character. In M/S mode, Ancora operates on Mid/Side components, measuring and controlling the relative level difference between Side and Mid signals. This enables active correlation control, allowing you to shape stereo correlation into a desired range. An optional RePhase function in M/S mode provides phase & energy compensation, maintaining natural punch and presence while achieving stereo width control.

Unlike static stereo width controls, Ancora provides dynamic, frequency-dependent processing that adapts to the music. The system operates completely independently of input levels, providing true "set & forget" functionality. Through its three curve controls, you can define exactly how much processing is applied (Depth), how quickly it responds (Timing), and what threshold triggers correction (Target) — all varying across the frequency spectrum to match your source material.

Ancora can also be used as a frequency-dependent stereo width compressor — taming excessive width where it occurs while preserving the natural spatial character of your mix. Mixes processed with Ancora often feel more stable and focused without sounding narrower.

The bidirectional connection between sliders and curves employs an intelligent priority system to prevent feedback loops and ensure smooth operation:

When you adjust the main slider (Depth, Timing, or Target), the corresponding curve handles update proportionally while maintaining their relative positions. Conversely, when you modify individual curve handles, the main slider automatically reflects the average of all active points.

This system uses a priority mechanism that gives precedence to the most recent user action. Whether adjusting via the plugin GUI or through DAW automation, Ancora ensures that intended changes are applied without conflicts or unwanted feedback. For automation purposes, it is recommended to use the main sliders (Depth, Timing, Target) rather than individual curve points. Hold Shift while dragging the master slider to activate multiplicative scaling mode, preserving the relative proportions of curve points. (When dragging individual curve handles, Shift instead locks the frequency — see Curve Editing.)

Additional options can be accessed using the standard context menu. This is opened by Right-clicking on a blank area anywhere in the UI. A click outside of the menu closes it.

• Shortcuts… — opens the keyboard shortcuts configuration dialog.
• User Interface Scale — selects one of the three size presets defined in the settings dialog.
• Instance — rename the specific plug-in instance.
• Copy State (Ctrl + C) — copies the current control states to the clipboard.
• Paste State (Ctrl + V) — pastes the control states from the clipboard.
• Share State — opens a dialog with sharing options via e-mail or forums.

Default shortcuts:

• Active (toggle): E
• Delta (toggle): D
• Depth (− / +): Q / W
• Timing (− / +): A / S
• Target (− / +): Y / X
• RePhase (− / +): R / T
• Bands (− / +): F / G
• Width (− / +): B / V

Step keys increment or decrement the parameter using snap values for stepped control.

Ancora was conceived and developed by Jan Ohlhorst.
Documentation by Shane Johnson.

Software evaluation by:

Ady Connor, Aleksi Vuolevi, Andrew Boult, Audiobomber | Castlemastering, Bob Olhsson, Cyril Meysson, Dan Suter | echochamber, Dan Worrall, Dax Liniere | Puzzle Factory, Dean, Dennis J Wilkins | Studio 12 Below, Diogo C. Borges, Eden Puder, Eric Recourt, EvilDragon, Greg Reierson, Gregg Janman | Hermetech Mastering, Helmut Erler | mastering.heyrec.org, Ilya Orlov, Janne Hatula, Jean Dante, Jeffrey Rippe, Jerry Anthony Mateo, Joe Caithness Mastering, Joseph Lyons, Justin Perkins, Laurent Sevestre, Michael Wynne, Miro Pajic, Murray Campbell | Beatworld, Niklas Silen, Nil Hartman, Pete Grandison, Resoundsound Mastering, Rich Prewett, Richard Pentrose, Robi Bulesic, Roland Löhlbach, Ruairi O'Flaherty, Sean Diggins, Sergey Makeev, Thaddeus Moore | Liquid Mastering, Titanio Studios, Valentin Zvukofor, Vitaly Zolotarev.