Neural DSP Quad Cortex Usage Guide

Expert guidance for using the Quad Cortex device library in MIDI Markdown files.

When to Use This Skill

Invoke this skill when working with:

Neural DSP Quad Cortex guitar processor
Quad Cortex preset loading and scene switching
QC expression pedal automation
Stomp footswitch control
Looper X control
Quad Cortex MIDI timing issues
Live performance automation for QC

Quick Start

Import the Library

mml

@import "devices/quad_cortex.mmd"

Basic Preset Loading

mml

[00:00.000]
# Load Setlist 1, Group 0, Preset 5
- qc_load_preset 1 0 0 5

# Or use simplified version (first 128 presets)
- qc_load_preset_simple 1 0 5

Scene Switching

mml

[00:16.000]
# Switch to Scene B
- qc_scene_b 1

# Or use parameterized version
- qc_scene 1 1

Critical Known Issues

1. Scene Switching Latency (100-130ms)

Problem: MIDI scene changes via CC#43 have significant latency in CorOS 2.0+

Symptoms:

Scene changes lag behind backing tracks
Timing sync issues in DAW automation

Workarounds:

mml

# Workaround 1: Send scene change early (in DAW)
[00:15.900]  # 100ms before the beat
- qc_scene 1 2

# Workaround 2: Use expression swell to mask latency
[00:16.000]
- qc_scene_with_swell 1 2  # Fades expression to hide latency

# Workaround 3: Enable "Ignore Duplicate PC" in device settings

System Recommendations:

Enable "Ignore Duplicate PC" in Quad Cortex MIDI Settings
Use -50ms track delay compensation on MIDI tracks in DAW
Send scene changes 1/16 note early

2. Rapid MIDI Messages Can Freeze Device

Problem: Sending rapid successive CC messages can freeze the device

Critical: ALWAYS add minimum 100ms delays between CC messages

Safe Expression Automation:

mml

# ❌ WRONG - No delays, can freeze device
[00:00.000]
- cc 1.1.0
- cc 1.1.42
- cc 1.1.85
- cc 1.1.127

# ✅ CORRECT - Use safe helper with enforced delays
[00:00.000]
- qc_exp1_step_automation 1

# ✅ CORRECT - Use safe ramp helper
[00:00.000]
- qc_exp1_safe_ramp 1 0 127

3. MIDI Thru is Broken

Problem: When MIDI Thru is enabled, device stops sending its own MIDI messages

Solution:

Keep MIDI Thru OFF
Use external MIDI merger if you need to combine signals

4. Preset Loading Timing Requirements

Critical: Must wait 100ms between Bank/Setlist/PC messages

mml

# ✅ CORRECT - qc_load_preset includes proper delays
[00:00.000]
- qc_load_preset 1 0 0 5

# This expands to:
# - cc 1.0.0      # Bank group
# [+100ms]
# - cc 1.32.0     # Setlist
# [+100ms]
# - pc 1.5        # Preset

Never manually construct this sequence without delays!

5. Expression Pedal MIDI Latency

Problem: CC#1/CC#2 have noticeable lag compared to physical pedals

Recommendations:

❌ Avoid MIDI for real-time wah or volume control
✅ Use physical expression pedals connected to EXP 1/2 jacks
✅ Use MIDI expression for slow parameter changes only
✅ Pre-programmed automation is acceptable

Preset and Scene Management

Complete Preset Load Sequence

mml

[00:00.000]
# Full preset load (group 0, setlist 2, preset 10)
- qc_load_preset 1 0 2 10

# Simplified (first 128 presets)
- qc_load_preset_simple 1 2 10

# Preset + Scene combo
- qc_load_preset_scene 1 2 10 3  # Load preset 10, scene D

Scene Control

mml

[00:00.000]
# Named scenes (A-H)
- qc_scene_a 1
- qc_scene_b 1
- qc_scene_c 1

# Parameterized (0-7 for scenes A-H)
- qc_scene 1 3  # Scene D

# Scene change with expression swell (masks latency)
- qc_scene_with_swell 1 4  # Scene E with crossfade

Stomp Footswitch Control

Basic Footswitch Control

mml

[00:00.000]
# Explicit on/off (64+ = active, 0-63 = bypass)
- qc_stomp_a_on 1
- qc_stomp_b_on 1

[00:08.000]
- qc_stomp_a_off 1

# Toggle mode (any value toggles)
- qc_stomp_c 1 127  # Toggles footswitch C

Emergency Cutoff

mml

[02:00.000]
# Bypass all footswitches (song ending)
- qc_all_stomps_off 1

Expression Pedal Control

Basic Expression

mml

[00:00.000]
# Direct MIDI value (0-127)
- qc_exp1 1 64

# Percentage (0-100)
- qc_exp1_percent 1 50

# With modulation curves
- qc_exp1_swell 1 0 127       # Smooth swell with ease-in-out
- qc_exp1_fade_in 1            # 0 to 127 with exponential curve
- qc_exp1_fade_out 1           # 127 to 0 with logarithmic curve

Advanced Expression Modulation

mml

[00:00.000]
# Vibrato effect using wave modulation
- qc_exp1_vibrato 1 64 5.5 10  # Center=64, freq=5.5Hz, depth=10%

# Tremolo effect
- qc_exp1_tremolo 1 64 4.0 30  # Center=64, freq=4Hz, depth=30%

# ADSR envelope
- qc_exp1_envelope 1

# Attack-Release envelope
- qc_exp1_ar 1 0.5 1.0  # Attack=0.5s, Release=1.0s

Looper X Control

Basic Looper Workflow

mml

[00:00.000]
# Open looper
- qc_looper_open 1

[+150ms]
# Start recording (momentary: send 127 then 0)
- qc_looper_record 1
[+100ms]
- qc_looper_stop 1

# Switch to playback
[+4s]
- qc_looper_play 1

# Close when done
[+8s]
- qc_looper_close 1

Safe Looper Workflow

mml

[00:00.000]
# Complete workflow with safe timing
- qc_looper_safe_workflow 1

Looper Features

mml

[00:00.000]
# Toggle features
- qc_looper_reverse 1      # Enable/disable reverse
- qc_looper_halfspeed 1    # Enable/disable half speed
- qc_looper_oneshot 1      # Enable/disable one shot
- qc_looper_undo 1         # Undo/redo

# Set quantize (0=off, 1-8=beats, 9=16 beats)
- qc_looper_quantize 1 4   # 4 beat quantize

Tempo and Tuner

Tempo Control

mml

[00:00.000]
# MIDI value (0-127)
- qc_tempo 1 64

# BPM (40-300)
- qc_tempo_bpm 1 120

Tuner Control

mml

[00:00.000]
# Toggle tuner
- qc_tuner_on 1
[+5s]
- qc_tuner_off 1

Mode Switching

mml

[00:00.000]
# Switch modes
- qc_mode_preset 1    # Preset mode
- qc_mode_scene 1     # Scene mode
- qc_mode_stomp 1     # Stomp mode

# Temporary mode switch
- qc_temp_stomp_mode 1 35 0  # Switch to stomp, toggle FS A, return to preset

Advanced Workflow Macros

Complete Song Section Change

mml

[00:00.000]
# Load preset, scene, and set expression
- qc_song_section 1 2 10 3 100
# Params: channel, setlist, preset, scene, exp1_value

DAW Initialization

mml

[00:00.000]
# Configure QC for DAW control
- qc_daw_init 1

# This enables:
# - Ignore Duplicate PC
# - Stomp mode
# - Closes Gig View
# - Disables tuner

Connection Recommendations

MIDI Connection Best Practices

Preferred: 5-pin DIN MIDI cables

More reliable than USB MIDI
Lower latency
Better isolation

If using both:

Disconnect USB when using DIN to prevent conflicts
Turn off MIDI Thru when using with DAWs

DAW Integration:

Disable MIDI Timecode (MTC) to prevent random preset changes
Disable MIDI Chase for CC messages
Enable "Ignore Duplicate PC" in Quad Cortex
Use specific MIDI channels, not "All"

Common Mistakes and Fixes

Mistake 1: Rapid CC Updates Without Delays

mml

# ❌ WRONG - Can freeze device
[00:00.000]
- cc 1.1.0
- cc 1.1.32
- cc 1.1.64
- cc 1.1.96
- cc 1.1.127

# ✅ CORRECT - Use safe helper
[00:00.000]
- qc_exp1_safe_ramp 1 0 127

Mistake 2: Scene Change Without Latency Compensation

mml

# ❌ WRONG - Will be late
[00:16.000]
- qc_scene 1 2

# ✅ CORRECT - Send early or use crossfade
[00:15.900]  # 100ms early
- qc_scene 1 2

# Or use crossfade helper
[00:16.000]
- qc_scene_with_swell 1 2

Mistake 3: Missing Delays in Preset Load

mml

# ❌ WRONG - Manual sequence without delays
[00:00.000]
- cc 1.0.0
- cc 1.32.2
- pc 1.10

# ✅ CORRECT - Use helper with built-in delays
[00:00.000]
- qc_load_preset 1 0 2 10

Performance Tips

Reliability Checklist

✅ Enable "Ignore Duplicate PC" in device settings ✅ Use MIDI DIN cables instead of USB for live performance ✅ Turn off MIDI Thru on the device ✅ Add 100ms spacing between all CC messages ✅ Keep firmware updated but test before gigs ✅ Use safe expression automation aliases

Mode Strategy

Recommended: Stay in Stomp Mode

Use CC#43 for scene changes even while in Stomp Mode
Creates "8x8 hybrid" control (8 stomps × 8 scenes)
Use temporary mode switching for specific needs

Expression Strategy

Connect physical expression pedals directly:

Avoid MIDI CC#1/CC#2 for real-time wah/volume
Use MIDI expression for slow parameter changes only
Always include timing delays between expression updates
Use qc_exp1_safe_ramp and similar helpers

Reference

Device Library Location

devices/quad_cortex.mmd

Documentation

Official MIDI Spec: https://support.neuraldsp.com/hc/en-us/articles/360014480320-MIDI-Specification
MIDI PC Calculator: https://support.neuraldsp.com/help/quad-cortex-midi-pc-calculator

Firmware Version

CorOS 3.2.1 (as of library version 1.0.0)

Troubleshooting

Issue	Solution
Scene changes are late	Enable "Ignore Duplicate PC", send early, or use crossfade
Device freezes with CC	Add 100ms delays, use safe automation helpers
Expression pedal is laggy	Use physical pedals, not MIDI CC
Preset won't load	Check timing delays (100ms minimum)
MIDI conflicts	Disable MIDI Thru, use specific channels
Random preset changes	Disable MIDI Timecode in DAW