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RonDamon666
User level: Level 1 (4 points)

AKM320 USB MIDI keyboard not detected after macOS 27 update

After updating to macOS 27, my AKM320 USB MIDI keyboard stopped working. It worked fine before the update with the exact same cable, hub, and port configuration.


Current behavior:

  • The AKM320 lights turn on, so it is getting power.
  • It does not appear in Audio MIDI Setup → MIDI Studio, even after clicking Rescan MIDI.
  • It does not appear in System Information → USB. When I unplug and replug it, no new USB device shows up at all.


Troubleshooting already tried:

  • Cable and controller are known good (same setup worked before the update).
  • Moved the com.apple.MIDI...plist files from ~/Library/Preferences/ByHost into a backup folder, then rebooted. No change.
  • Reconnected the AKM320 and opened MIDI Studio. The device is completely gone.
  • Confirmed in System Report → USB that macOS is not detecting it at the USB data level, only providing power.

What I suspect:

This looks like the reported CoreMIDI / MIDI 2.0 bug in macOS 27. Many USB MIDI devices either stop responding, get stuck notes, or disappear entirely from CoreMIDI. In some cases they don’t even show up under USB in System Report.


Questions:

  • Is anyone else seeing this with USB MIDI devices on macOS 27?
  • Is there any known fix or workaround besides downgrading to macOS 26?
  • Any Terminal commands, plist resets, or CoreMIDI tricks that have worked for you?

I’m trying to avoid erasing or downgrading anything until I know there’s no safer fix. Any help would be appreciated.


System: MacBook Air M2, macOS 27

Device: AKM320 USB MIDI keyboard

Connection: USB hub (same config worked before update)

Posted on Oct 6, 2026 6:29 PM

1 reply

neuroanatomist
User level: Level 9 (72,871 points)

Oct 16, 2026 9:06 AM in response to RonDamon666

The CoreMIDI and Web MIDI bugs in macOS 27 (Golden Gate) have been reported. The issue stems from Apple's updated MIDI 2.0 implementation with older class-compliant MIDI 1.0 hardware data. Because the OS misinterprets the initialization data handshake, it chokes before the device tree can even register it under System Information -> USB.


Before you decide to downgrade or wipe your system, several targeted workarounds have successfully restored USB MIDI functionality for affected users:


Force a "Clean Studio Reconnect" (Hub Isolation)

While your hub config worked on macOS 26, macOS 27 handles initial USB handshakes differently.

  • Disconnect your USB hub and all peripherals from your MacBook Air.
  • Restart the computer.
  • Plug the AKM320 directly into the MacBook Air's port using a simple USB-C to USB-A adapter (bypassing the multi-port hub completely).
  • Why this works: macOS 27 has known power/data allocation bugs over third-party multi-port hubs; isolating the keyboard forces the CoreMIDI server to evaluate only that device handshake. 


Bypass CoreMIDI 2.0 with a Legacy Router (MidiPipe)

If the hardware is still blocked at the OS layer, some musicians are using MidiPipe or Bidule to catch and translate the raw hardware messages before CoreMIDI misinterprets them.

  • Download the latest version of MidiPipe. 
  • Go to System Settings → Privacy & Security and click Open Anyway if macOS 27 blocks the legacy tool.
  • Launch MidiPipe; it can often bridge class-compliant devices directly through its own MIDI 1.0 pipeline, allowing your DAW to see the tool as a MidiPipe Input rather than an OS-level device. 


Clear the CoreMIDI Driver Cache via Terminal

Since plist deletion didn't work, try forcefully killing the CoreMIDI background daemon to clear out the corrupted device state.

  • Open Terminal (find in Spotlight or Applications > Utilities) and execute:
sudo killall -9 MIDIServer
  • Type your Mac login password when prompted (nothing will appear on the screen, type carefully) then press return
  • Immediately after running this, plug the keyboard in while holding down its octave buttons (if your model supports a hardware hard reset on power-up) to trigger a clean USB registration.


Create a Fresh MIDI Studio Configuration

  • Open Audio MIDI Setup → Window → Show MIDI Studio.
  • At the top, click the Configuration drop-down menu and choose New Configuration....
  • Name it, click OK, and let the system build a completely fresh routing index without any remnants of your previous macOS 26 hardware layout.


More info from Apple: If a connected MIDI device isn’t shown in Audio MIDI Setup on Mac - Apple Support


Reportedly, major audio developers like Steinberg and Morningstar have noted that they are collaborating with Apple on an update.


Originally posted at discussions.apple.com/thread/256371583