I'm running Windows 11 24H2 - 26100.7840, and a few days ago noticed that Loop Midi Ports were not being recognised by other apps. forums.steinberg.net Loop Midi hidden in Windows 11 25H2 fix - Steinberg Forums

The "story" of loopMIDI on Windows 11 is one of a long-standing Tobias Erichsen essential tool meeting a massive operating system overhaul. For years, loopMIDI has been the go-to for creating virtual MIDI ports, but the recent introduction of has introduced both new features and some growing pains. 1. The Classic Setup

If you compose music in software like MuseScore or Sibelius but want to use the high-end instrument libraries hosted in your DAW: Create two ports: Score_Out and Daw_In .

Your DAW freezes, crashes, or the loopMIDI data counter spikes into millions of bytes instantly.

Windows 11 now allows for native loopback, which can be configured through the Microsoft MIDI GitHub repository . This is recommended for long-term compatibility, although it requires setting up specific "loopback endpoints."

This is the simplest and most effective immediate fix:

Check the box for and Autostart loopMIDI . This ensures your virtual ports are always active whenever you boot up your computer. Creating and Managing Virtual Ports

If your computer freezes or a DAW track starts lagging violently, you might have created a MIDI feedback loop. This happens when an application is accidentally set to both receive from and send to the exact same loopMIDI port simultaneously, causing an infinite loop of data.

The only official source for loopMIDI is Tobias Erichsen's website. Navigate to the official page: https://www.tobias-erichsen.de/software/loopmidi.html . Click on the "Download" link to get the latest version of the setup executable (a .exe file).

Verify that the output of Software A is matched exactly to the input of Software B, and that both are using the same loopMIDI port.