Sibelius Error 40207 Fixed: How to Resolve the MIDI Memory Glitch

Sibelius error 40207 displays a message stating there is not enough memory available. However, this has absolutely nothing to do with your computer RAM.

This error triggers when Sibelius cannot access your MIDI keyboard because another application has locked the port. Simply closing conflicting DAWs or updating your MIDI drivers resolves the issue.

WARNING: Do NOT purchase more RAM, increase your page file, or alter your system memory settings. The 40207 not enough memory message is a legacy MMSYSTEM/IN false flag. It strictly means your MIDI input device is blocked by another program.

What Causes Sibelius Error 40207?

Error 40207 typically appears right after the Initializing Playback Configuration screen during startup. The software attempts to connect to your configured MIDI input device but hits a blocked pathway. Consequently, the legacy audio engine throws the inaccurate memory shortage message.

The most frequent culprit is a Digital Audio Workstation running in the background. Programs like Cubase or Studio One often monopolize the MIDI keyboard inputs exclusively. Therefore, when Sibelius tries to share that same device, the audio driver refuses access.

Older MIDI interfaces and outdated USB drivers compound this issue significantly. Many older devices use single-client drivers where only one application communicates with the hardware. Furthermore, conflicting ASIO or WASAPI audio configurations can artificially lock the MIDI ports.

Trigger	Background Cause	Error Message Variant
DAW Running	Cubase or Studio One has locked the MIDI port	Not enough memory (MMSYSTEM/IN)
Single-Client Drivers	MIDI interface cannot split signals to two apps	Not enough memory
USB Power Drop	USB Hub lacks power to initialize the MIDI device	Device failed to open
ASIO/WASAPI Conflict	Basic MIDI config clashes with advanced audio drivers	Not enough memory
ReWire Slave Mode	Host DAW fails to release the MIDI lock	Not enough memory

Fix 1: Close or Reconfigure Conflicting DAWs

If you run Sibelius simultaneously with a DAW, you must manage shared MIDI data. Sibelius often fails to open the MIDI device simply because your DAW grabbed it first. Therefore, closing the DAW completely before launching Sibelius is the fastest diagnostic test.

If you need both applications open for a ReWire session, you must adjust preferences. Specifically, you must disable the MIDI keyboard input inside your DAW settings. By freeing the port, Sibelius can successfully claim the hardware during startup.

Similar to fixing a JDownloader content offline error, software conflicts require isolating the background process. You must stop other programs from hoarding the active data stream.

1. Save your work and completely close Cubase, Studio One, or your active DAW.
2. Verify the DAW is fully closed via the Windows Task Manager.
3. Launch Sibelius and wait for the Playback Configuration to initialize.
4. If the error disappears, the DAW was locking the MIDI port.
5. To run both, open your DAW MIDI settings and disable the keyboard input.
6. Relaunch Sibelius with the port now available.

Fix 2: Unplug and Reroute Your MIDI Keyboard

Sometimes, the Windows audio subsystem traps the MIDI port in a ghost loop. The operating system incorrectly thinks an application is using the keyboard. Fortunately, a simple hardware reset forces Windows to drop the lock.

USB hubs are notorious for causing initialization failures in Sibelius. Unpowered USB splitters often fail to provide the exact voltage needed for a MIDI handshake. Consequently, the Sibelius engine interprets this failed connection as error 40207.

Rerouting your keyboard directly to the motherboard bypasses these hub bottlenecks. You should also ensure you plug the device into a high-speed rear USB port. Just as hardware diagnostics solve a Samsung washer error 4C code, checking physical connections resolves digital failures.

1. Close Sibelius completely.
2. Unplug your MIDI keyboard USB cable from your computer.
3. Restart your computer to clear the Windows audio cache.
4. Plug the MIDI keyboard directly into a rear motherboard USB port.
5. Do not use an external USB hub, monitor passthrough, or keyboard passthrough.
6. Launch Sibelius and test the MIDI input connection.

HARDWARE NOTE: Always plug MIDI interfaces directly into the motherboard. We have seen hundreds of MMSYSTEM errors resolved simply by ditching cheap, unpowered USB splitters.

Fix 3: Update to Multi-Client MIDI Drivers

If you absolutely must use your MIDI keyboard in multiple apps, you need upgrades. Specifically, your hardware needs modern multi-client drivers installed. A multi-client aware MIDI driver allows the OS to duplicate signals to multiple programs.

Unfortunately, many older MIDI keyboards rely on generic Windows drivers. These class-compliant generic drivers are strictly single-client. Therefore, you must visit your keyboard manufacturer’s website and download their proprietary software package.

1. Identify the exact model number of your MIDI keyboard or interface.
2. Visit the manufacturer’s official support website.
3. Download the latest dedicated Windows drivers for your hardware.
4. Install the new drivers and restart your PC.
5. Open Sibelius and navigate to the Input Devices menu.
6. Select your newly named hardware driver instead of the generic Windows MIDI option.

Fix 4: Check ASIO and WASAPI Settings

Conflicting audio playback protocols can accidentally disable your MIDI inputs entirely. If you use advanced audio drivers alongside a Basic MIDI configuration, Sibelius often crashes. Ultimately, the routing engine gets confused between the two audio protocols.

You must ensure your Audio Engine Options align properly with your Input Devices. Switching your playback device away from a locked ASIO driver frees MIDI bandwidth. Updating legacy files like an Intel VGA driver package similarly resolves old system conflicts.

1. Launch Sibelius, unplugging your keyboard first if the app refuses to open.
2. Go to the Play tab and click the small arrow to open the Setup dialog.
3. Click on Audio Engine Options.
4. Look at your current Interface setting, which might be ASIO, WASAPI, or DirectSound.
5. Change the interface to a different protocol, such as Primary Sound Driver.
6. Plug your keyboard back in, restart Sibelius, and test the connection.

Frequently Asked Questions

The questions below address common confusion regarding Sibelius error 40207. We base these answers on verified solutions from official Avid support forums. Additionally, we consulted the broader Avid Sibelius troubleshooting community.

Does error 40207 mean my computer needs more RAM?

No. The error message explicitly says not enough memory available, but this is entirely false. It is a legacy error code from the MMSYSTEM engine indicating a blocked MIDI port.

Why does this error happen when using Studio One or Cubase?

DAWs like Studio One and Cubase automatically lock MIDI inputs exclusively by default. When Sibelius attempts to access the same MIDI keyboard during startup, it gets denied access.

Can I run Sibelius and a DAW at the same time?

Yes, but you need a multi-client MIDI driver from your keyboard manufacturer. Alternatively, you must go into your DAW settings and disable the MIDI input device.

Why does unplugging my keyboard fix the error?

Unplugging the keyboard forces the Windows operating system to drop background software locks. Replugging it creates a fresh connection that Sibelius can claim during its startup sequence.