MIDI API Mode Switcher

1. What this tool is

Windows 11 ships with a new MIDI stack called Windows MIDI Services. For compatibility, Microsoft included a switch that lets users fall back to the legacy MIDI implementation. That switch is a single value in the registry, and Microsoft's official guide asks users to add it by hand using regedit.exe.

This tool does exactly the same thing, but removes the opportunities for mistakes — it writes to the correct key, uses the correct data type, only accepts valid values, and reminds you to restart when it's done.

2. Which mode to pick

3. How to use it

1. Launch MidiApiModeSwitcher.exe

   Just double-click it. Launching does not trigger a User Account Control (UAC) prompt, so you can safely check the current status without any elevated permissions.

2. Read the "Current Status" box

   The box at the top shows the current mode, the registry value, the MIDI service status, and whether the new MIDI stack is installed. Look at it before you switch, so you know what changed afterwards.

3. Pick the mode you want to switch to

   Click Mode 0, Mode 1, or Mode 2. The colored block below updates in real time with notes about that mode — green means recommended, orange means it has caveats, red means diagnostics only.

4. Click "Apply Changes"

   A confirmation dialog appears first; only after you confirm will the UAC prompt ask for administrator rights. This is the only step in the whole flow that requires elevation. If you click "No" on the UAC prompt, the tool returns quietly without making any change.

5. When the reminder dialog appears, click "OK"

   Once the write succeeds, a small dialog will pop up to remind you that the change is not yet in effect and that a restart is required.

   

   Clicking "OK" only closes the dialog and does nothing else. This tool does not restart your computer for you, so any unsaved work is safe.

6. Restart the computer yourself

   Save your work first, then restart Windows yourself. Without a restart the setting will not take effect — there is no workaround; see the next section.

   After you dismiss the reminder, the main window keeps showing "change saved, not yet in effect" in orange until you restart, so you won't forget.

4. How to confirm the switch worked

What the main window looks like after applying, before restarting

After you close the reminder dialog with "OK", the main window keeps reminding you that a restart is still pending:

Method 1: Confirm with the tool itself (easiest — recommend this to customers)

After restarting, run MidiApiModeSwitcher.exe again and look at the "Current Status" box at the top:

Before it reads the service status, the tool enumerates the MIDI ports once via the MIDI 1.0 API. This is exactly the check Microsoft's official documentation recommends — "run a MIDI 1.0 application, then check whether midisrv is running". So the color of this line has a specific meaning:

Method 2: Confirm with PowerShell commands

If you want to verify it yourself, or you're walking a customer through it remotely, open PowerShell and run:

# Currently stored mode (no output = not set = Mode 0)
(Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32').UseLegacyMidi

# Current state of the MIDI service
Get-Service midisrv | Select-Object Name, Status

The first line tells you what the setting says; the second tells you what is actually running. You have to read them together:

Method 3: Look at the registry directly

Open regedit.exe and paste this path into the address bar:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32

Look for UseLegacyMidi on the right. This method only confirms what the setting is; it cannot confirm whether it is in effect. Use it only to rule out "the value never got written".

Method 4: Judge by actual behavior

After switching to Mode 1, you should observe the following changes. If none of them happened, the mode is not yet in effect:

5. Troubleshooting

The tool shows "Running — abnormal, mode not in effect"

This is the most common situation, and it has exactly two causes:

MIDI devices disappeared after switching

First, confirm you actually switched to Mode 1 and not Mode 2. Under Mode 2 (Hybrid) the new and old drivers can't see each other's devices, so ports come and go depending on the application — this is the expected behavior of that mode, not a bug. Switch back to Mode 0 or Mode 1.

If a device is missing under Mode 1, check whether another application is already holding that port open. Legacy mode has no multi-client support: one port can only be opened by one application at a time.

"Windows protected your PC" appears when I launch it

That's SmartScreen warning you about an unsigned program. Click "More info" → "Run anyway" to continue. If you obtained this tool from an official source, this warning does not mean the file is bad.

I clicked "Apply Changes" and nothing happened

Check that you clicked "Yes" on the UAC prompt. If you clicked "No", the tool returns quietly, changes nothing, and does not show an error message — that is intentional, so as not to alarm users. Click "Apply Changes" again to retry.

How to get all the way back to factory settings

Pick Mode 0 and apply. The tool removes the UseLegacyMidi value outright instead of writing it as 0 — both are functionally identical, but removing it returns the machine to a factory-clean state. A restart is still required.

6. For support agents: the diagnostic report

The "Copy diagnostic info" button at the bottom of the tool copies the full system state to the clipboard. Have the customer click it and paste the result straight into the support ticket — that beats ten rounds of clarifying questions.

=== MIDI API Mode Diagnostics ===
Machine        : DESKTOP-XXXXXXX
OS             : Windows 11 Home 25H2 (build 26200.8973)
Registry path  : HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32
UseLegacyMidi  : (not set)
Effective mode : 0 (Full Windows MIDI Services)
midisrv        : Running
Drivers32 midi : wdmaud.drv
Drivers32 midi1: wdmaud2.drv
MIDI Services  : installed, in use
Elevated       : no

MIDI inputs (0):
  (none)

MIDI outputs (1):
  [0] Microsoft GS Wavetable Synth

How to read this report