This is just a quick post here to assist users with known issues or workarounds, in the interest of remaining transparent on this project.
Main Windows MIDI Services Announcement blog post
The issues and workarounds here apply only to the new Windows MIDI Services rollout in Windows 11 retail 24h2 and 25h2. This does not apply to older versions of Windows. Insider builds get different releases on a different schedule so this information may or may not apply to a Windows Insider Canary/Dev/Beta release.
We performed a ton of testing with customers, partners, and our own equipment over the development cycle for Windows MIDI Services, but some bugs have made it through, as is known to happen with software development. We’re working on them in priority order, but I wanted to ensure the most impactful ones have more detail here.
Full issue list and updates for bugs may be found on our GitHub Repo
Info: How do I know if the new Windows MIDI Services Stack is enabled?
Windows MIDI Services is part of a Phased Rollout. This means that after you install the KB which contains the Windows MIDI Services binaries, you will get the new feature enabled at some point in the next month. Who gets enabled depends on the algorithms that control the rollout phases.
To see if your PC has the new Windows MIDI Services feature enabled, go to https://aka.ms/midi and download the checker tool there. It will be up until the next SDK release, where it will be included as part of the SDK and Tools package. Run this checker and pay attention to the output. It will tell you if the new stack has been enabled on your PC as part of the phased rollout. If it says it has not been enabled, then you are still running the older Windows MIDI stack, and any issues are unrelated to this release of Windows MIDI Services.
There is no way for customers to force enablement of the Windows MIDI Services stack. Everyone who has installed the KB update will be enabled by the end of February as part of the phased rollout. Uninstalling the KB update(s) is the only way to disable the new MIDI stack.
Bug: Dynamic ports (loopMIDI, loopBE, virtualTE / teVirtualMIDI / rtpMIDI) are not always visible.
Problem: Third-party drivers which dynamically create MIDI ports in Windows do not work as before. Unless the ports were created before the service was started, they are not visible. Additionally, if you have more than 16 loopback ports defined in either loopBE or loopMIDI, only 16 will be available, and the names may be messed up.
Known to affect:
- loopMIDI
- loopBE / loopBE30
- teVirtualMIDI (used by loopMIDI as well)
- Sonic Core software-defined MIDI ports
- te rtpMIDI
Possibly impacts
- SSL 360 link
- MPC Live III
The problem is that the devices create the ports after midisrv has already started, and we don’t currently detect new ports added to an existing device. So what the next workaround is doing is trying to get the dynamic ports created before midisrv asks for them, and before you start your MIDI-using apps.
The MIDI Service today detects only when new devices are created, not when existing devices create new ports. This will be fixed. (Currently expected for 4th week of March release 3D)
Workaround 1: Ensure you have 16 or fewer ports defined, and then restart the service
Close all apps using MIDI. Plug in any devices needed and create the ports in the tool and then restart the MIDI Service through either the Services app or the command line. The service shows up as “Windows MIDI Service” and is named midisrv. You can right-click and select “restart”, or if it’s not running, “start”.
Administrator command prompt method:
- Create your MIDI ports in the third-party tool.
- Close all MIDI apps
- Open Windows Terminal as an Administrator (“run as administrator”)
- Type
net stop midisrv - After that completes, type
net start midisrv - Start up the app you want to use with MIDI
Workaround 2: Use the built-in loopbacks instead
Only if you see that Windows MIDI Services is enabled, you can download the SDK Runtime and Tools package (it is currently unsigned and so you will receive several warnings) and then install it. Do not install this if Windows MIDI Services is not already enabled on your PC as it will cause issues with existing MIDI 1.0 apps and MIDI 2.0 devices, and your new loopback endpoints will not work at all.
This will install the MIDI and Musician Settings app. In that app, the first-run experience will prompt you to complete setting up MIDI. Part of that includes creating some default loopback endpoints. You can create as many other loopback endpoints as you need after the initial setup has created a configuration file for you.
Please pay attention to how these bidirectional loopbacks work, using the information provided in the MIDI Settings app Loopbacks page when you create a loopback endpoint. Loopback A sends to Loopback B. Loopback B sends to Loopback A.
Of course, this will only work for you if what you need are loopback endpoints.
Bug: Apps using the WinMM MIDI 1.0 API may not see newly plugged-in devices.
If you connect or power on a USB MIDI device after you’ve already started an app using the older WinMM MIDI 1.0 API, the device may not be visible.
This can also be true of browser-based MIDI apps.
Workaround 1: Plug in your MIDI device early
Plug in the MIDI device and ensure it has fully booted up before starting the app.
Workaround 2: Use more than one MIDI device
If you plug in multiple MIDI devices, apps will receive the notification that new devices have been added.
Workaround 3: Restart the MIDI Service
Exit the application, plug in the device, and restart the MIDI service as described in the first issue. This level of restart is not normally required unless there are custom drivers in use which dynamically create MIDI ports.
Bug: Apps using the WinMM MIDI 1.0 API may crash if you disconnect or power down a plugged-in device
If you disconnect, power down, or otherwise restart a USB MIDI device while an app is using it, that application may crash, depending upon how it has opened the device. This may also required a reboot to clear, depending upon the application.
Workaround:
Wait until the app has exited before unplugging or powering down a device. This also applies to dynamically-created devices that are not physical USB devices.
Bug: VirtualDJ Not able to communicate with controller
We have worked with VirtualDJ on this, and would like to thank them for their cooperation and quick response.
The new MIDI stack is much faster than the old one, so we’re finding that some apps are running into errors that they hadn’t previously run into. In the case of VirtualDJ, this results in the UI freezing up.
We’ll have a broader fix in Windows. In the meantime, VirtualDJ have released their Build 9005 with a fix for this. You can download it from their main download page, or let your copy of VirtualDJ update itself.
If that doesn’t fix it for you, you can uninstall the KB update.
Issue: Korg devices using a .DRV winmm-style driver are not recognized
The new Windows MIDI Services stack does not recognize the older-style .DRV WinMM drivers. Luckily, there’s very little need for them anymore as the new stack is fully multi-client and supports class-compliant USB MIDI devices. There is no plan to change this behavior.
Fix (only if Windows MIDI Services is already enabled on your PC)
Completely uninstall and remove the driver. This can be tricky with the Korg drivers in-particular because they tend to cause issues in the registry. A full article is coming on this and will be linked here when ready.
- Uninstall the Korg driver
- Physically disconnect the MIDI device
- In Device Manager (you can find the device manager by right-clicking the start button and selecting it), in the view menu, choose “Show hidden devices”
- Go down to “Sound, video and game controllers, find the device
- Right-click the grayed-out device you just found. Choose “uninstall device”
- If prompted to completely remove the driver, select the option to do so.
- Reboot
After the reboot, the device should be reassigned to our in-box MIDI driver. However, the uninstaller run earlier may have messed up the registry. In that case, download the latest SDK Runtime and Tools package (and only that package) and install it. Once installed, open an Administrator command prompt or terminal window and type midifixreg. Follow the prompts if any. If any changes were made, you will need to reboot again.
These are the only required registry entries for Windows MIDI Services.
How to uninstall the update if needed
The first KB update containing the new Windows MIDI Services stack started rolling out during the last week of January, as the January 2026 Feature Update Preview (KBKB5074105). If you need to uninstall that, look for it in Settings > Windows Update > Update History > Uninstall Update
Future updates may also include this feature and so will need to be handled separately.
Other Important Notes
Do not use the Korg Driver Uninstaller or any other tool which works to change the ordering of midi…midi9 entries in the registry. Windows MIDI Services requires only that midi is set to wdmaud.drv and midi1 is set to wdmaud2.drv. If those two entries are not present, Windows MIDI Services will not work on your system. The SDK runtime and tools includes a tool midifixreg which will ensure these two settings exist, in case you’ve already run one of these tools on your system.
How to File Bugs or Report Issues
Please do not comment on this post with issues/bugs/questions.
Questions/Discussion, and for customers without access to GitHub, issue reporting: https://aka.ms/mididiscord
Developers and anyone else with access to GitHub can file issues here: https://aka.ms/midirepoissues
Hello Pete, i’m in trouble. loopMIDI was working correctly, but this morning it disappeared from the system. I’m on the latest Windows 11 25H2 release and I use a Stream Deck with Ableton. I had been struggling with this issue because I was on a Windows Beta version. I managed to install the official Windows release, and everything worked correctly for two weeks. This morning loopMIDI disappeared again.
I haven’t installed any new hardware or drivers, except for my graphics card drivers. I uninstalled loopMIDI, cleaned the registry, and reinstalled it, but nothing changed — loopMIDI is not detected in Device...
Hi Roberto
Blog comments aren’t any good for debugging an issue, and I’d need much more info to help you out. Can you join https://aka.ms/mididiscord and create a new thread under midi-user-questions please?
Pete
Microsoft
Hi Pete,
> after you install the KB which contains the Windows MIDI Services binaries, you will get the new feature enabled at some point
Does it mean we get another one update that will enable the Windows MIDI Services? If not, how it will be done? I hope MS cannot remotely manage my PC 🙂
Updates can be enabled or pulled if, for example, it turns out it’s breaking PCs, or in this case, to control the pace of a feature rollout.
I do not know what that mechanism looks like or exactly how it works, but it’s likely through Windows Update.
Pete