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MIDI Output Troubleshooting

This guide helps you diagnose and resolve common issues with Conductor’s MIDI output functionality, including SendMIDI actions, virtual MIDI ports, and DAW integration.

Quick Diagnostic Checklist

Before diving into specific issues, run through this quick checklist:

  • Virtual MIDI port is created and online (IAC Driver, loopMIDI, ALSA)
  • DAW has MIDI input enabled for the virtual port
  • Conductor config specifies the correct port name (case-sensitive)
  • MIDI messages are being sent (check conductor --verbose logs)
  • DAW is receiving MIDI (check DAW’s MIDI monitor)
  • Correct MIDI channel is used (usually Channel 0)
  • No other applications are blocking the MIDI port

Common Issues

Issue 1: “Port not found” Error

Symptoms:

ERROR: MIDI output port "IAC Driver Bus 1" not found
Available ports: []

Possible Causes:

  1. Virtual MIDI port not created or offline
  2. Port name mismatch (case-sensitive)
  3. Conductor started before port was created
  4. Permissions issue (Linux/Windows)

Solutions:

macOS (IAC Driver)

  1. Verify IAC Driver is online:

    # Open Audio MIDI Setup
open -a "Audio MIDI Setup"
    • Window → Show MIDI Studio
    • Double-click IAC Driver
    • Check “Device is online”
    • Click Apply

  2. List available MIDI ports to verify the exact name:

    # Use conductor diagnostic tool
cargo run --bin test_midi

  3. Restart Conductor daemon:

    conductorctl stop
conductor

Windows (loopMIDI)

  1. Verify loopMIDI is running:

    • Check system tray for loopMIDI icon
    • If not running, launch loopMIDI from Start Menu

  2. Verify port exists in loopMIDI:

    • Open loopMIDI application
    • Ensure at least one port is listed (e.g., “Conductor Virtual”)

  3. Check exact port name (case-sensitive):

    • Note the exact name shown in loopMIDI
    • Update config.toml to match exactly: 
      [modes.mappings.action.then_action]
type = "SendMIDI"
port = "Conductor Virtual"  # Must match exactly

  4. Restart Conductor:

    conductorctl stop
conductor

Linux (ALSA)

  1. Verify virtual MIDI port exists:

    aconnect -l

    Look for “Virtual Raw MIDI” or similar.

  2. Load ALSA virtual MIDI module if missing:

    sudo modprobe snd-virmidi

  3. Verify port name and update config:

    # List MIDI ports
aconnect -l

    Update config.toml with the exact port name.

  4. Permissions (if port access denied):

    # Add user to audio group
sudo usermod -a -G audio $USER

# Log out and log back in for changes to take effect

Issue 2: Messages Sent But Not Received by DAW

Symptoms:

  • Conductor logs show messages being sent
  • DAW doesn’t respond (no transport control, no parameter changes)
  • No error messages

Diagnosis:

  1. Enable verbose logging in Conductor:

    conductor --verbose

    Look for lines like:

    [DEBUG] Sending MIDI: NoteOn(note=60, velocity=100, channel=0) to port "IAC Driver Bus 1"

  2. Check DAW’s MIDI monitor:

    • Logic Pro: View → Show MIDI Environment → Monitor
    • Ableton Live: Preferences → Link, Tempo & MIDI → MIDI Ports (check Track/Remote enabled)
    • Reaper: View → MIDI Device Diagnostics

Possible Causes & Solutions:

Cause 1: DAW MIDI Input Not Enabled

Logic Pro:

  1. Open Logic Pro → Settings → MIDI → Inputs (⌘,)
  2. Locate your virtual MIDI port
  3. Check the box to enable it
  4. Close Settings

Ableton Live:

  1. Open Preferences → Link, Tempo & MIDI
  2. In MIDI Ports section, find your virtual port
  3. Enable Track and Remote for the input port
  4. Close Preferences

Reaper:

  1. Open Preferences → MIDI Devices
  2. Find your virtual MIDI port in the input list
  3. Enable Enable input from this device
  4. Click OK

Cause 2: Wrong MIDI Channel

Solution: Most DAWs use Channel 0 (sometimes labeled as “Channel 1” in DAW UI). Verify your config:

[modes.mappings.action.then_action.message]
type = "NoteOn"
note = 60
velocity = 100
channel = 0  # Change to match DAW expectations

Test different channels (0-15) to find the correct one.

Cause 3: Wrong CC Numbers or Note Numbers

Solution: Use DAW’s MIDI Learn feature to discover correct values:

Logic Pro:

  1. Logic Pro → Control Surfaces → Learn Assignment
  2. Click the parameter to control
  3. Note the CC number shown (update your config)

Ableton Live:

  1. Click MIDI button (top-right, or press ⌘M)
  2. Click the parameter to control
  3. Press your MIDI controller (Ableton learns the mapping)
  4. Note the CC/Note number (if you want to replicate in config)

Cause 4: Control Surface Conflicts

Solution: Disable conflicting control surfaces in DAW:

Logic Pro:

  • Logic Pro → Control Surfaces → Setup
  • Disable any control surfaces using the same MIDI port

Ableton Live:

  • Preferences → Link, Tempo & MIDI
  • In Control Surface section, ensure no conflicting surface is assigned to the same port

Issue 3: Latency / Delayed Response

Symptoms:

  • Noticeable delay (>50ms) between pad press and DAW response
  • Audio/MIDI feels “laggy”

Possible Causes & Solutions:

Cause 1: High Audio Buffer Size

Solution: Lower DAW’s audio buffer size:

Logic Pro:

  1. Logic Pro → Settings → Audio
  2. Reduce I/O Buffer Size to 128 or 64 samples
  3. Note: Lower buffer = lower latency, but higher CPU usage

Ableton Live:

  1. Preferences → Audio
  2. Reduce Buffer Size to 128 or 64 samples

Reaper:

  1. Preferences → Audio → Device
  2. Reduce Block size to 128 or 64 samples

Cause 2: Third-Party Virtual MIDI Drivers

Windows: loopMIDI adds ~5-10ms latency. This is usually acceptable, but if critical:

  • Consider rtpMIDI (network MIDI) for even lower latency
  • Ensure loopMIDI is up to date

macOS: Use IAC Driver (native, near-zero latency) instead of third-party apps.

Linux: Use ALSA virtual ports (native, low latency) instead of JACK MIDI (higher latency).

Cause 3: System CPU Load

Solution:

  1. Close unnecessary applications
  2. Freeze/bounce tracks in DAW to reduce CPU usage
  3. Increase audio buffer size if CPU is maxed out (trade latency for stability)

Cause 4: Conductor Processing Delay

Diagnosis: Check Conductor logs for processing time:

conductor --verbose

If you see warnings about slow processing, check:

  1. Complex velocity curves (use simpler curves)
  2. Conditional actions with many conditions (simplify)
  3. Sequence actions with many steps (reduce)

Solution: Simplify mappings to reduce processing overhead.

Issue 4: Messages Sent to Wrong Port

Symptoms:

  • DAW receives MIDI from a different source
  • Conductor logs show correct port, but DAW sees different port

Possible Causes & Solutions:

Cause 1: Multiple Virtual MIDI Ports

Solution: List all available MIDI ports and verify exact name:

# Use Conductor diagnostic tool
cargo run --bin test_midi

Update config to use the correct port name (case-sensitive):

[modes.mappings.action.then_action]
type = "SendMIDI"
port = "IAC Driver Bus 1"  # Not "IAC Driver Bus 2"

Cause 2: Port Name Changed

macOS (IAC Driver):

  • If you renamed the bus in Audio MIDI Setup, update your config

Windows (loopMIDI):

  • If you renamed the port in loopMIDI, update your config
  • Restart Conductor after renaming

Issue 5: Velocity Not Working

Symptoms:

  • All MIDI messages sent with same velocity (e.g., always 127)
  • Velocity curves not being applied

Possible Causes & Solutions:

Cause 1: Fixed Velocity in Config

Problem: Config specifies a fixed velocity value:

[modes.mappings.action.then_action.message]
type = "NoteOn"
note = 60
velocity = 127  # Fixed velocity
channel = 0

Solution: Use a velocity curve to map input velocity:

[modes.mappings.action.then_action.message]
type = "NoteOn"
note = 60
channel = 0

[modes.mappings.action.then_action.message.velocity_curve]
type = "PassThrough"  # Use controller velocity directly

Cause 2: Trigger Doesn’t Capture Velocity

Problem: Trigger type doesn’t include velocity information.

Solution: Use a trigger that captures velocity:

[modes.mappings.trigger]
type = "Note"  # Captures velocity
note = 1
# Velocity is automatically available to velocity_curve

Issue 6: Virtual Port Not Visible in DAW

Symptoms:

  • Virtual MIDI port exists (verified via OS tools)
  • DAW doesn’t list the port in MIDI preferences

Possible Causes & Solutions:

macOS (IAC Driver)

Cause: DAW started before IAC Driver was enabled.

Solution:

  1. Enable IAC Driver in Audio MIDI Setup
  2. Restart the DAW
  3. Alternatively: Logic Pro → Settings → MIDI → Reset MIDI Drivers

Windows (loopMIDI)

Cause: DAW doesn’t detect dynamically created ports.

Solution:

  1. Create loopMIDI port before launching DAW
  2. If DAW is running, restart it after creating the port

Linux (ALSA)

Cause: ALSA virtual port created after DAW startup.

Solution:

  1. Load snd-virmidi module before launching DAW: 
    sudo modprobe snd-virmidi
  2. Restart DAW
  3. Alternatively: Use aconnect to manually connect ports

Platform-Specific Issues

macOS Specific

IAC Driver “Device is offline” After Reboot

Problem: IAC Driver unchecks itself after macOS reboot.

Solution:

  1. Open Audio MIDI Setup
  2. Double-click IAC Driver
  3. Check “Device is online”
  4. This should persist, but if not, consider using an AppleScript to auto-enable on login

Permissions Issues with HID Device

Problem: Conductor can’t access MIDI controller hardware.

Solution:

  1. Grant Input Monitoring permissions:
    • System Settings → Privacy & Security → Input Monitoring
    • Enable for Terminal (if running cargo run)
  2. Restart Conductor

Windows Specific

loopMIDI Port Disappears

Problem: loopMIDI port intermittently disappears.

Solution:

  1. Ensure loopMIDI is set to start with Windows:
    • Right-click loopMIDI tray icon → Settings → Start with Windows
  2. If port disappears, restart loopMIDI application
  3. Restart Conductor daemon

Multiple MIDI Drivers Conflict

Problem: Multiple virtual MIDI drivers (loopMIDI, rtpMIDI, etc.) cause conflicts.

Solution:

  1. Use only one virtual MIDI driver at a time
  2. Disable/uninstall unused drivers
  3. Assign unique port names if using multiple drivers

Linux Specific

ALSA Permissions Denied

Problem: Conductor can’t access ALSA virtual MIDI ports.

Solution:

# Add user to audio group
sudo usermod -a -G audio $USER

# Log out and log back in

# Verify group membership
groups | grep audio

JACK MIDI vs ALSA

Problem: DAW uses JACK MIDI, but Conductor uses ALSA.

Solution:

  1. Bridge ALSA to JACK using a2jmidid: 
    sudo apt-get install a2jmidid
a2jmidid -e &
  2. Use qjackctl to route ALSA virtual port to JACK
  3. Alternatively: Use JACK-native virtual MIDI ports instead of ALSA

Advanced Debugging

Enable Conductor Debug Logging

Run Conductor with verbose logging to see detailed MIDI output:

conductor --verbose

What to look for:

  • [DEBUG] Sending MIDI: ... - Confirms messages are being sent
  • [ERROR] Port not found: ... - Port name issues
  • [WARN] Slow processing time: ... - Performance issues

Monitor MIDI Traffic in DAW

Logic Pro:

  1. View → Show MIDI Environment
  2. Click Monitor object
  3. Watch for incoming MIDI messages

Ableton Live:

  1. Preferences → Link, Tempo & MIDI
  2. Enable Track and Remote for the port
  3. Create a MIDI track
  4. Arm the track for recording
  5. Watch the MIDI input meter

Reaper:

  1. View → MIDI Device Diagnostics
  2. Select your virtual MIDI port
  3. Watch for incoming messages

Test MIDI Loopback

Create a loopback test to verify MIDI output is working:

  1. Route virtual output back to Conductor input (macOS):

    • Audio MIDI Setup → IAC Driver
    • Create two buses: “Conductor Out” and “Conductor In”
    • Configure Conductor to send to “Conductor Out”
    • Configure Conductor to receive from “Conductor In”
    • Use a MIDI routing app to bridge them

  2. Send a test message:

    # Press a pad and verify it's received on the input
conductor --verbose

Getting Help

If you’ve tried all troubleshooting steps and still have issues:

  1. Gather diagnostic information:

    # List MIDI ports
cargo run --bin test_midi > midi_ports.txt

# Run Conductor with verbose logging
conductor --verbose 2>&1 | tee conductor_debug.log

# (Press pads to trigger actions)

# Stop after 30 seconds
conductorctl stop

  2. Check configuration:

    cat ~/.config/conductor/config.toml

  3. Report the issue:

    • GitHub: https://github.com/amiable-dev/conductor/issues
    • Include:
      • Platform (macOS, Windows, Linux)
      • Conductor version (conductor --version)
      • DAW name and version
      • MIDI port name
      • Relevant config.toml sections
      • Debug logs (conductor_debug.log)
      • midi_ports.txt

See Also