Sequential Fourm Firmware Update
If you have a Sequential Fourm synthesizer and you notice problems with aftertouch in the lowest octave of keys, it’s not a hardware problem with the keyboard. It’s a small bug, and there’s a firmware update that you can install that will fix the issue. Here are our instructions.
- Sequential Fourm Keys OS v1.0.0.2 Firmware Update
- Checking Your Installed OS Version
- Overview of Updating the Firmware
- Firmware Update Procedure
- Need Help? Contact Support
Sequential Fourm Keys OS v1.0.0.2 Firmware Update
Sequential has two separate firmwares in their unit, called the OS Main and the Keys OS. This note is concerned with updating the Keys OS.
This update is to fix an issue that won’t affect all units. The error occurs on the bottom C – F keys. If the polyphonic aftertouch on these keys gets “stuck on max” or is not sensitive to pressure, then install this firmware update.
Checking Your Installed OS Version
To view the currently installed versions:
Turn on the Fourm.
- Press the Global button in the Program module.
- Turn the Select knob clockwise to reach the OS page.
- You’ll see version numbers for the Main and the Keys OS.
As of this notice, on February 3, 2026, the newest version of the Main is 1.0.0.1 and the current version of the Keys OS is 1.0.0.2.
If your versions are lower than these, you’ll need to perform the firmware update.
Overview of Updating the Firmware
Here is an overview of Sequential’s instructions.
The Fourm update is performed using MIDI SysEx (system exclusive) data.
On your Windows or Mac computer, you download the firmware updater SysEx file from the Sequential website.
Then you connect your Fourm to your computer using a USB-C data cable.
To accomplish the transfer, you need a third-party shareware app on your computer that reads the SysEx file from your computer and uploads the MIDI data to your Fourm over the USB cable. Use MIDI-OX on Windows or SysEx Librarian on macOS.
[While it’s possible to use a 5-pin DIN MIDI cable to connect your Fourm to a MIDI-to-USB interface to your computer, and while it may be possible to transfer SysEx through a DAW, it’s more straightforward to use the USB port and either of these apps, so that’s the method we recommend.]
When the SysEx data is transferred to your Fourm, it will initiate the update process.
Here are the detailed steps.
Firmware Update Procedure
Install MIDI-OX for Windows or SysEx Librarian for macOS
MIDI-OX for Windows and SysEx Librarian for macOS
On your Windows PC, go to the MIDI-OX website, download the newest version of the app, and follow the installation instructions.
If you are on macOS, go to the Snoize.com SysEx Librarian website and do likewise.
Download the Firmware Updater from Sequential
On your computer, go to the Sequential Fourm Operating System download page.
Download the Keys OS v1.0.0.2 installer file.
The updater will arrive as a .zip file. Locate it in your Downloads folder. Extract the .zip file and you will see the SysEx file, named Fourm_Key_v1.0.0.2.syx.
You’ll also see the Fourm OS Installation Instructions.txt document. This has detailed instructions that you’ll want to review.
Set the Fourm to Receive MIDI SysEx
On the Fourm:
- Press the Global button in the Program module to enter the Global Settings menu.
- Scroll through to page 19: MIDI SysX.
- Press the Select knob to select and change the value to On.
- Press the Select knob again to return to the Global Settings menu.
- Using the Select knob, turn to page 20: MIDI SysX Port.
- Press the Select knob to change the value to USB.
- Press Program to leave Global Settings and save the changes.
Disconnect any MIDI cables from your Fourm.
Connect the Fourm directly to your computer using a USB-C data cable and a USB adapter if needed.
On Your Computer
IMPORTANT: Be patient during the firmware update procedure. Do not disconnect the USB cable, do not shut down the MIDI app, do not shut down your computer, and do not shut down the Fourm until the display on the Fourm prompts you to restart the unit. Doing any of these will cause the update to fail.
Whether you are on macOS or Windows, close your DAW and all other apps that use MIDI, and disconnect any other MIDI devices or interfaces connected to your computer.
On macOS
Open the SysEx Librarian app.
- Choose Fourm from the Destination menu.
- Click Add/+. An Open dialog will appear.
- Browse to and open the file named Fourm_Key_v1.0.0.2.syx that you downloaded from the Sequential website. The file name appears in the file list and should be highlighted.
- Click the Play button to transmit the file.
On the Fourm, the display will say “Receiving OS…” with a percentage amount. When the transfer completes, the display will say “Do not turn off power! Receiving OS. Updating OS.”
Once installed, the screen will say “Finished updating. Turn power off & back on now to use this OS.”
Power off the unit using the rear power button. Turn it back on.
The firmware update should now be installed.
Troubleshooting for SysEx Librarian
If the countdown stops before the file transfer is complete, turn the synth off, then on, and repeat the procedure on your Mac with SysEx Librarian.
If the countdown continues to fail, it may be because the transmission speed is too high.
In SysEx Librarian, under Preferences, click on Transmit Speed and reduce the speed. Then close the Preferences window and try transmitting the file again.
If the problem persists, try reducing the speed further.
On Windows
Open the MIDI-OX app.
- From the Options menu, choose Configure Buffers.
- Set the Low Level Output Buffers Num and Size to 1024.
- Click OK to close the window and save the settings.
- From the Options menu, choose MIDI Devices.
- In the lower-left quadrant of the window, select the MIDI port to which the instrument is connected. If the connection is via USB, choose Fourm.
- Click OK to close the window and save the settings.
- From the View menu, choose SysEx.
- From the Command Window menu, choose Send SysEx.
- Browse to and open the file named Fourm_Key_v1.0.0.2.syx that you downloaded from the Sequential website.
- From the Command Window menu, choose Send SysEx.
On the Fourm, the display will say “Receiving OS…” with a percentage amount. When the transfer completes, the display will say “Do not turn off power! Receiving OS. Updating OS.”
Once installed, the screen will say “Finished updating. Turn power off & back on now to use this OS.”
Power off the unit using the rear power button. Turn it back on.
The firmware update should now be installed.
Troubleshooting for MIDI-OX
If the installation stops or stalls before the file transfer is complete, turn the synth off, then on again, and repeat the procedure on your PC with MIDI-OX.
If the countdown on the Fourm continues to fail, change the settings on MIDI-OX. Double the Low Level Output Buffers Num and Size values and re-send the SysEx file.
If the countdown gets closer to zero, then you know your settings are moving in the right direction.
If the countdown goes further, try reducing the Num and Size values.
You can also try doubling or quadrupling the Size setting.
You may have to adjust the Low Level Output Buffers settings several times before finding the right combination.
Need Help? Contact Support
If you bought your Sequential Fourm from Sweetwater and you need help, don’t hesitate to contact our Support staff through our support contact page or by phone at (800) 222-4700.
You can also contact Sequential Support at this link.
Sweetwater’s Daniel Fisher demos the Sequential Fourm
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