[BUG]: Some USB MIDI port of MIDI 1.0 device of which the number of Input ports and output ports differs seem not to work when using USBMidi2-ACX.

Report pre-requisites

• I have searched this repo for existing issues to confirm this is not a duplicate
• I agree to follow this project's Code of Conduct

Clarity and Disclosure

• I confirm that any AI analysis included in this report is clearly called out / tagged as AI-generated with "AI Generated Content". Reports with suspected AI content may be closed if not disclosed.
• I confirm that I will quickly follow-up to questions or requests for additional detail, otherwise the issue may be closed

Windows Version

Windows 11 Pro 25H2 26200.8737 (confirmed in 26200.8524)

Type of bug

• Windows doesn't recognize MIDI device (doesn't show in device manager)
• Application doesn't recognize MIDI device or ports
• Cannot update firmware on MIDI device (specify device, app, and firmware info)
• MIDI device is recognized, but cannot send or receive messages
• Sent or received MIDI messages are corrupted
• Application not working as expected
• MIDI 1.0 ports not named as expected
• Performance not as expected
• Localization issue (incorrect or missing language for Windows running something other than en-US)
• General application crash or hang
• MIDI Service crash or hang requiring Windows reboot
• Windows bugcheck / BSOD (please include in the areas below the device id from Windows Settings About page or a link to your crash dump uploaded to a sharing service)
• Other or Unsure (please indicate in additional notes section below)

Location

• Application using WinMM MIDI 1.0 (Classic API). Name provided below.
• Application using WinRT MIDI 1.0 (Windows 10 MIDI). Name provided below.
• Application using Windows MIDI Services SDK (MIDI 2.0). Name provided below.
• Other app/DAW/tool. Not sure about which API or SDK it uses. Name provided below.
• Windows MIDI Services tools like MIDI Settings, Console, etc.
• Directly in Windows MIDI Services SDK (for Developers only, please provide repro code)
• General Windows shell (Device Manager, Settings, Services, etc.). Name provided below.
• Windows MIDI 2.0 Class Driver (usbmidi2-acx)
• Windows MIDI 1.0 Class Driver (usbaudio)
• Vendor-provided MIDI driver (please provide details below)
• Other or Unsure (please indicate in additional notes section below)

Application Name and Version

Pocket MIDI 64-bit (MIDI1.0 API), midi.exe (MIDI 2.0)

MIDI Device Name

reported below: KORG SQ-1 (same bug is confirmed: KORG RK-100S 2, KORG tritonTaktile)

Output from the MIDI Diagnostics Tool

tmpbdymc3.tmp.txt

Repro

• I confirm that I was able to reproduce this issue using a simple app like midi.exe, midi1monitor.exe or Pocket MIDI
• I tried but was unable to reproduce this issue using a simple application

Steps to reproduce

*In this report, use MIDI Setting App 1.0.17-rc.4.25 and newer-style port names.

KORG SQ-1 has 1 MIDI Input port and 2 MIDI Output ports (see below MIDI Settings screen shot):

When using USBMidi2.sys, the output port "SQ-1 _ CTRL" (Mapped Group 2) seems not to work and both messages from Win MM App.
In default USBMidi2.sys is installed for SQ-1 when connecting to PC, so as a result 1 output port is not available.

=================
repro:

1. connect SQ-1 to PC via USB.
2. Launch Pocket MIDI 64-bit and open output port "SQ-1 _ CTRL".
3. send some messages (see below):

4. Capture these messages by analyzer. In the result, there are no "OUT" messages.

There is no problem when using USBAUDIO.sys.

=================
The same phenomena are happened for these devices of which the number of Input ports and output ports differs:
KORG RK-100S : 1 input port and 2 output ports
-> the output port "RK-100S _ SOUND" (Mapped Group 2) seems not to work.

KORG TRITON taktile series: 2 input ports and 3 output ports
-> the output port "TR taktile-25 _ MIDI I/F OUT" (Mapped Group 3) seems not to work.

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Expected behavior

All ports are available correctly.

Additional notes

KORG SQ-1 issue reported in the Discord seems to be caused by the same issue.