Harmonic Sweetener

The Harmonic Sweetener is a 7-band mastering processor designed to bring depth, cohesion, and polished harmonic character to your finished tracks and mixes. It combines surgical multiband saturation, intelligent genre-matching analysis, smart macros, and a full preset & A/B comparison system.

Mastering Features & Workflow

Unlike standard distortion or saturation plugins, the Harmonic Sweetener is built specifically for full mixes and master busses where phase integrity, precision crossover filtering, and tonal balance are paramount.

1. Target Profiles & Reference Track Matching

To help you dial in a professional tonal balance, the plugin includes a built-in profile matching engine:

• 20+ Genre Profiles: Select a target profile tailored for your genre (EDM, Techno, House, Drum & Bass, Hip-Hop, Pop, Rock, Metal, Jazz, Classical, Acoustic, Lo-Fi, Synthwave, and more).
• Reference Track Analyzer: Select Reference Track and load your favorite commercial master (WAV, MP3, FLAC, OGG, AIFF). The engine will analyze the reference track across all 7 frequency bands and match its spectral contour.
• Learn & Match (4-Pass Analysis): Press ▶ Learn & Match while playing your track. The engine runs a 4-pass real-time calibration:
  1. Pass 1: Analyzes dynamic range and tonal balance to calibrate smart macro targets.
  2. Pass 2: Selects and fine-tunes harmonic saturation models per band.
  3. Pass 3: Evaluates the master output curve.
  4. Pass 4: Automatically matches loudness to target LUFS while engaging the True Peak limiter.

2. Smart Mastering Macros

Once your baseline is set, 12 macro knobs allow intuitive musical adjustments across your mix without having to tweak dozens of individual band parameters:

• Low End & Warmth:
  • Sub Weight: Adds physical low-end weight to sub frequencies (Band 1).
  • Bass Punch: Enhances the kick and bass punch in the low-mid spectrum (Band 2).
  • Warmth: Imparts gentle analog tube warmth across lower mids.
  • Mud Removal: Dynamically clears out boxiness and clutter around 250Hz–400Hz.
• Presence & Highs:
  • Presence: Pushes vocals, guitars, and leads forward in the mix.
  • Clarity: Opens up detail and separation in the high-midrange.
  • Air: Gentle top-end sparkle (Band 7) with perceived loudness compensation.
  • Harmonic Bias: Shifts between even-order (tube/warmth) and odd-order (grit/tape) harmonics.
  • Tape Hiss: Optional vintage analog noise floor.
• Dynamics & Glue:
  • Density: Adds master bus glue and harmonic saturation density.
  • Punch Preserve: Ensures transients cut through dense saturation stages.
  • Smoothness: Tames harsh resonances across all bands.
  • Re-Match LUFS: One-click button to snap your master back to target loudness after adjusting macros.

3. 7-Band Multiband Engine & Visualizers

Underneath the macros, you have full access to individual frequency bands:

• 7 Split Bands: Crossover frequencies can be freely adjusted or set to standard Linkwitz-Riley LR4 or zero-phase Linear Phase modes.
• Per-Band Processing: Choose from 12AX7 Tube, Triode, Transformer, Tape, or Subtle Drive per band with independent compression, gate, and Mid/Side (M/S) stereo balancing.
• Integrated Metering: Includes a real-time Spectrum Analyzer, LUFS Loudness Meter (Integrated, Short-term, Momentary), Stereo Vectorscope / Phase Correlation meter, and True Peak Limiter with Gain Reduction readout.

4. Presets & A/B Testing

• Browser & Navigation: Browse categorized presets by genre or quickly cycle with the < and > buttons.
• JSON Presets: Save custom setups with 💾 Save As (stored as portable JSON files in ~/.config/MultiHarmonicSweetener/Presets/).
• A/B Toggle & History: Compare two mastering states instantly with the [ A ] / [ B ] switch, backed by multi-level Undo/Redo.

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Built with Rust, NIH-plug, and egui. Tested on Debian Trixie (RT-Kernel), Bitwig Studio 6, and Carla.