CurveAndDrag

📘 Overview

CurveAndDrag is a professional stereo delay and pitch shifter module for VCV Rack featuring analog-inspired DSP, comprehensive tape delay modeling, and advanced microtonal tuning support. Combining four distinct pitch shifting algorithms with multi-head tape delay emulation, cross-channel feedback, and extensive CV automation, CurveAndDrag delivers studio-grade delay effects with vintage character and modern precision.

🚀 Key Features

• Four Pitch Shifting Algorithms: BBD (Bucket Brigade), H910 (Harmonizer), Varispeed (Tape), and Hybrid modes
• Multi-Head Tape Delay: 1-4 configurable tape heads with authentic wow/flutter modeling
• Independent Stereo Processing: Separate left/right delay times, feedback, and detune controls
• Comprehensive Tape DSP: Saturation, aging, instability, noise (0-8%), and head EQ
• Advanced Quantization: 11 built-in scales plus MTS-ESP and Scala file support
• Tempo Sync: Musical subdivisions (1/1, 1/2, 1/4, 1/8, 1/8T, 1/16) with tap tempo
• Cross-Channel Feedback: Stereo enhancement with progressive limiting
• Extensive CV Control: 21 CV inputs for complete automation
• Real-Time Displays: Subdivision, scale, tuning info, and 5-segment level meters
• Professional Layout: 48HP module with logical 6-section organization

🎛 Parameters and Controls

Core Delay Parameters

Parameter	Type	Range	Default	Description
Time L	Knob	0-2000ms	200ms	Left channel delay time
Time R	Knob	0-2000ms	200ms	Right channel delay time
Feedback L	Knob	0-110%	30%	Left channel feedback amount
Feedback R	Knob	0-110%	30%	Right channel feedback amount
Mix L	Knob	0-100%	50%	Left channel dry/wet mix
Mix R	Knob	0-100%	50%	Right channel dry/wet mix
Cross-Feedback	Knob	0-100%	0%	Cross-channel feedback amount

Tempo Sync & Subdivision

Parameter	Type	Range	Default	Description
Sync L	Toggle	On/Off	Off	Left channel tempo sync enable
Sync R	Toggle	On/Off	Off	Right channel tempo sync enable
Subdiv L	Selector	0-5	2	Left subdivision (1/1, 1/2, 1/4, 1/8, 1/8T, 1/16)
Subdiv R	Selector	0-5	2	Right subdivision (1/1, 1/2, 1/4, 1/8, 1/8T, 1/16)

Pitch Shifting System

Parameter	Type	Range	Default	Description
Main Pitch	Knob	±2 octaves	0	Global pitch shift in cents
Detune L	Knob	±50 cents	0	Left channel fine detune
Detune R	Knob	±50 cents	0	Right channel fine detune
Detune Drift	Knob	0-25 cents	0	Stereo detune movement
Pitch Mode	Selector	0-3	1	Algorithm: BBD/H910/Varispeed/Hybrid
Character	Knob	0-100%	50%	Vintage pitch shifter modeling
Morph	Knob	0-100%	0%	Blend between pitch algorithms

Scale & Tuning

Parameter	Type	Range	Default	Description
Quantize	Toggle	On/Off	Off	Enable pitch quantization
Scale Select	Selector	0-10	0	Built-in scale selection
MTS-ESP	Toggle	On/Off	Off	External tuning source enable

Built-in Scales: 12-TET, 24-TET, 31-EDO, Just Intonation, Pythagorean, Meantone, Well-Tempered, 19-TET, 22-TET, 53-TET, 72-TET

Tape DSP Engine

Parameter	Type	Range	Default	Description
Tape Mode	Toggle	On/Off	Off	Enable tape delay processing
Saturation	Knob	0-100%	30%	Tape saturation amount
Aging	Knob	0-100%	0%	Vintage wear and frequency response
Instability	Knob	0-100%	0%	Speed variations and dropouts
Noise Enable	Toggle	On/Off	Off	Tape noise enable
Noise Amount	Knob	0-8%	0.8%	Tape noise level
Head Config	Selector	1-4	1	Number of active tape heads

Modulation (Wow & Flutter)

Parameter	Type	Range	Default	Description
Wow Rate	Knob	0.1-5.0 Hz	0.3 Hz	Wow oscillation rate
Wow Depth	Knob	0-100%	20%	Wow modulation depth
Flutter Rate	Knob	1.0-10.0 Hz	2.7 Hz	Flutter oscillation rate
Flutter Depth	Knob	0-100%	10%	Flutter modulation depth
Wow Waveform	Selector	0-2	0	Sine/Triangle/Random
Flutter Waveform	Selector	0-2	0	Sine/Triangle/Random

Head EQ System

Parameter	Type	Range	Default	Description
Head Bump Freq	Knob	60-120 Hz	90 Hz	Low frequency resonance
Head Bump Gain	Knob	0-3x	1.2x	Resonance gain
Rolloff Freq	Knob	3-15 kHz	10 kHz	High frequency rolloff
Rolloff Resonance	Knob	0.5-2.0	0.7	Rolloff Q factor

Gain Controls

Parameter	Type	Range	Default	Description
Input Gain	Knob	0-2x	1x	Input signal gain
Output Gain	Knob	0-2x	1x	Output signal gain

📶 CV Inputs

CV Input	Target Parameter	Range	Description
Input Gain CV	Input Gain	±10V	Input level modulation
Output Gain CV	Output Gain	±10V	Output level modulation
Time L CV	Left Time	±10V	Left delay time modulation
Time R CV	Right Time	±10V	Right delay time modulation
Feedback L CV	Left Feedback	±10V	Left feedback modulation
Feedback R CV	Right Feedback	±10V	Right feedback modulation
Mix L CV	Left Mix	±10V	Left mix modulation
Mix R CV	Right Mix	±10V	Right mix modulation
Time Mod CV	Global Time	±10V	Global time modulation (±100ms)
Feedback Mod CV	Global Feedback	±10V	Global feedback modulation (±10%)
Pitch CV	Main Pitch	±10V	Main pitch modulation (1V/oct scaling)
Detune L CV	Left Detune	±10V	Left detune modulation
Detune R CV	Right Detune	±10V	Right detune modulation
Detune Drift CV	Drift	±10V	Stereo drift modulation
Morph CV	Algorithm Morph	±10V	Pitch algorithm blending
Character CV	Character	±10V	Vintage modeling amount
Wow Rate CV	Wow Rate	±10V	Wow rate modulation
Wow Depth CV	Wow Depth	±10V	Wow depth modulation
Flutter Rate CV	Flutter Rate	±10V	Flutter rate modulation
Flutter Depth CV	Flutter Depth	±10V	Flutter depth modulation
Saturation CV	Saturation	±10V	Tape saturation modulation
Aging CV	Aging	±10V	Tape aging modulation
Instability CV	Instability	±10V	Tape instability modulation
Tape Noise CV	Noise Enable	±10V	Noise enable trigger
Noise Amount CV	Noise Amount	±10V	Noise level modulation
Head Select CV	Head Config	±10V	Head configuration selection

🔄 Signal Flow

Audio Input → Input Gain → Pitch Shifting → Delay Lines → Cross-Feedback → Tape Processing → Output Mix → Audio Output
     ↓              ↓            ↓              ↓              ↓              ↓              ↓
   Gain CV     Character CV   Pitch CVs     Delay CVs    Cross-FB Param   Tape CVs     Mix/Gain CVs

Detailed Flow:

1. Input Stage: Audio input with gain control and CV modulation
2. Pitch Processing: Four algorithms (BBD/H910/Varispeed/Hybrid) with quantization
3. Delay Processing: Independent L/R delay lines with tempo sync capability
4. Cross-Feedback: Filtered cross-channel feedback with progressive limiting
5. Tape Emulation: Comprehensive tape modeling (wow/flutter, saturation, aging, noise)
6. Output Stage: Dry/wet mixing with independent wet outputs and level metering

Key Signal Path Features:

• Independent stereo processing throughout entire chain
• Cross-feedback applied after delay but before tape processing
• Pitch shifting with automatic gain compensation
• Tape effects as final processing stage before output mixing
• Real-time level metering with 5-segment displays

📦 Installation

Automatic Installation

1. Download CurveAndDrag-1.0-WINDOWS-x64.vcvplugin from releases
2. Double-click to install in VCV Rack

Manual Installation (Windows)

1. Extract plugin contents to individual files
2. Copy to %APPDATA%/Rack2/plugins-win-x64/CurveAndDrag/:
   • plugin.dll
   • plugin.json
   • res/CurveAndDrag.svg

Dependencies

• VCV Rack 2.0 or higher
• Windows x64 (tested on Windows 10/11)
• Optional: MTS-ESP host for external tuning support

⚠️ Known Issues & Tips

Performance Notes

• Large Pitch Shifts: Shifts >±1 octave may introduce latency artifacts
• High Feedback: Feedback >90% requires careful gain staging
• Tape Instability: High instability values can cause temporary dropouts (by design)

Usage Tips

• Tempo Sync: Use tap tempo inputs for manual BPM detection
• Cross-Feedback: Start with low values (10-20%) to avoid resonance
• Tape Noise: 0-8% range provides authentic vintage character without masking signal
• Head Configuration: Multiple heads create rhythmic echoes with slight timing offsets
• Scale Quantization: Combine with external sequencers for microtonal composition

Limitations

• MTS-ESP: Requires separate MTS-ESP host plugin for external tuning
• Scala Files: Load via right-click menu, limited to 12-tone octave patterns
• Pitch Tracking: Optimized for tonal material, may not track percussion accurately

🧪 Testing & Validation

Verified Features

✅ All 37 parameters respond correctly to manual control
✅ All 21 CV inputs provide proper modulation ranges
✅ Tempo sync works with all 6 subdivision types
✅ All 4 pitch algorithms function with gain compensation
✅ Tape processing includes complete DSP chain
✅ Built-in scales quantize accurately
✅ Level meters respond to both input and output signals
✅ Cross-feedback stable at all settings

Test Patch Ideas

• Rhythmic Delays: Sync different subdivisions to create polyrhythmic patterns
• Pitch Harmonization: Use detune L/R with quantization for harmonic intervals
• Tape Character: Combine aging, saturation, and noise for authentic vintage sound
• Modulated Delays: Use wow/flutter with high depths for experimental textures
• Microtonal Sequences: Connect CV sequencer to scale selector for dynamic tuning changes

📖 Licensing & Credits

License: MIT License - see LICENSE file for details

Author: Joshua McDonagh
Email: josh.mcd31@gmail.com
GitHub: https://github.com/shua-ie/curveanddrag

Special Thanks:

• VCV Rack community for DSP optimization techniques
• MTS-ESP specification contributors for microtonal support
• Vintage tape delay manufacturers for authentic modeling references

📈 Version History

v1.0 (Current) - Initial Professional Release

• Complete 48HP professional layout with 6-section organization
• All 37 parameters fully functional with CV automation
• Enhanced tape DSP with proper 0-8% noise scaling
• Independent L/R pitch processing with gain compensation
• Real-time displays for subdivisions, scales, and tuning info
• Cross-feedback system with progressive limiting
• Professional parameter tooltips and status lighting
• Four pitch shifting algorithms (BBD/H910/Varispeed/Hybrid)
• Complete tape delay emulation with wow/flutter modeling
• 11 built-in scales plus MTS-ESP and Scala file support
• 21 CV inputs for comprehensive automation
• Tempo sync with musical subdivisions and tap tempo

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CurveAndDrag v1.0 - Professional Stereo Delay & Pitch Shifter for VCV Rack