The best sounding (most musical) module to date.
-o9.o9.26
The way it’s meant to be played:
Assign up to 16 AU’s to a unique midi channel (0-15)
Route all AU’s channels into SPECTR.
Play directly in SPECTR with your keyboard, feed a sequencer to it, and use the X\Y pad to play parts or just noodling.
Listen to example below, which only utilizes 4 channels, but can climb to 16.
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Unlock the resonant power of acoustic physics with the SPECTRAL CHORD ENGINE v2.0, a sick AF real-time harmonizer for Mozaic /AUM. Inspired by the 20th-century Spectralist movement of Gérard Grisey and Tristan Murail, this module transcends equal temperament by expanding single MIDI incoming notes into true, mathematically exact overtone and subharmonic series. Powered by a dynamic 16-channel pool that applies microtonal pitch bends to individual partials, v2.0 introduces real-time timbral morphing between held notes, customizable historical tuning filters, and organic shimmer modulation. Whether you are crafting shimmering microtonal pads, brooding subharmonic basslines, or evolving acoustic landscapes, the Spectral Chord Engine transforms your MIDI instruments into organic, living timbral ecosystems.
SPECTRAL CHORD ENGINE v2.0 — User Manual
Mozaic MIDI Script for iOS Audio Hosts (AUM Compatible)
Overview & Core Concept
The Spectral Chord Engine v2.0 converts incoming single-note MIDI messages into microtonally tuned harmonic structures based on true acoustic overtone or undertone series (f, 2f, 3f\dots or f, f/2, f/3\dots).
Rather than snapping to standard 12-Tone Equal Temperament (12-TET), the script calculates the precise logarithmic deviations (1200 \times \log_2(n)) required for natural harmonics—including non-standard intervals such as the flat 7th (~31 cents flat), quarter-tone 11th (~49 cents flat), and neutral 13th (~41 cents sharp). Each harmonic partial is dynamically assigned to its own MIDI channel (0–15) with an independent MIDI Pitch Bend message applied.
Critical Setup Requirements
To ensure proper microtonal tracking and polyphonic voicing, set up your iOS host (e.g., AUM) and destination synthesizer according to the following requirements:
MIDI Channel Routing: Your receiving synthesizer must be configured to receive and monitor all 16 MIDI Channels (Channels 1–16 / Index 0–15) simultaneously (MPE-style or Multi-Timbral).
Pitch Bend Range Alignment: Match the synth’s hardcoded internal Pitch Bend Range directly to the script’s Knob 2 (Bend Range) setting. If Knob 2 is set to 2 semitones, set your synthesizer’s pitch bend range to \pm 2 semitones.
Interface Controls
XY Pad
X Axis (Fundamental Octave Shift): Live register control (0 to 4 scale mapping to -2 to +2 octaves). Moving the X axis dynamically rebuilds all currently held chords at the new octave register.
Y Axis (Shimmer Depth): Controls the depth of the Expression (CC11) modulation applied when Shimmer mode is enabled.
Knob Controls
Knob 0 (Num Harmonics): Sets the requested number of partials per note (Range: 2 to 16).
Knob 1 (Filter): Filters which partials in the series are voiced:
0: All harmonics
1: Odd harmonics only
2: Even harmonics only
3: Every 3rd harmonic
Knob 2 (Bend Range): Sets the pitch bend calculation range in semitones (Range: 1 to 12). Must match destination synth setup.
Knob 3 (Base Vel): Base velocity for the primary fundamental note (Range: 0 to 127).
Knob 4 (Rolloff): Sets the natural acoustic velocity decay rate across ascending higher harmonics (Range: 0 to 100).
Knob 5 (Shimmer Rate): Determines the speed/metro division of the CC11 shimmer cycle (Range: 0 to 127).
Knob 6 (Tuning Reference): Selects the underlying microtonal reference system:
0 (Harmonic): True physical overtone/undertone cent deviations.
1 (Just Intonation): Snaps harmonic intervals to nearest 5-limit Just scale degrees.
2 (Pythagorean): Snaps harmonic intervals to nearest 3-limit Pythagorean scale degrees.
Knob 7 (Morph Rate): Sets the automatic crossfade speed between held notes when Spectral Morphing is triggered (0 = Off).
Pad Buttons
Pad 0 (ENGINE ON/OFF): Toggles script processing. Turning off sends a full Panic cutoff.
Pad 1 (SERIES Overtone/Undertone): Toggles between the ascending Overtone series and the mirror-image subharmonic Undertone series (f, f/2, f/3\dots). Automatically rebuilds held notes upon toggle.
Pad 2 (SHIMMER ON/OFF): Toggles independent CC11 phase-shifted amplitude breathing across active channels.
Pad 3 (PANIC / CLEAR): Immediately sends CC123 (All Notes Off), resets all 16 channel pitch bends to center (8192), and clears active note buffers.
Pad 4 (FORCE RELEASE ALL): Manual safety release button to send Note Off events specifically for active held chords without resetting globally.
Advanced Engine Features & Logic
1. Dynamic Channel Allocation & Fair Polyphony
Standard MIDI provides 16 discrete channels. Because every harmonic requires an independent pitch bend offset, the script dynamically distributes the 16 available channels across held notes using a “fairness cap” logic:
1 Note Held: Receives up to all 16 channels for a complete spectral stack.
2 Notes Held: Each note is capped at 8 channels maximum.
3+ Notes Held: Available channels are dynamically divided (\text{Cap} = \lfloor 16 / \text{Held Count} \rfloor). When notes are released, remaining notes automatically expand to claim freed channels and rebuild their voice stacks.
2. Spectral Morphing Mode
When exactly two notes are held and Knob 7 (Morph Rate) is set above 0:
The engine halts standard shimmer functions and initiates a CC11 expression crossfade between Note 1 and Note 2.
Over the tempo-synced cycle, Note 1’s partials fade out while Note 2’s partials fade in, causing the sonic timbre to morph seamlessly from one fundamental spectral signature to another.
3. Shimmer Modulation
When enabled via Pad 2, each active channel receives an out-of-phase CC11 triangle-wave modulation calculated during host tempo pulses (@OnMetroPulse). Each channel’s phase offset (\text{channel} \times 7) creates an evolving, breathing acoustic halo effect across the harmonic spectrum.
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REQUIREMENTS:
MIDI Channel Routing = Your receiving synthesizer must be configured to receive and monitor all 16 MIDI Channels (Channels 1–16 / Index 0–15) simultaneously (MPE-style or Multi-Timbral).