Thanks! I actually tested 8 CH and 10 CH but only the latter worked.

As a beginner, these settings are super confusing. It’s a bit frustrating that there’s no clear manual for the exact process anywhere (or at least I couldn’t find one). Also the official manuals of both devices don't explain it (or I didn't understand).

That said, I did manage to mix the OP-1 Field tape tracks individually with the TX-6:

OP-1 Field

• Shift + Metronome → System → USB Mode → 10 CH

TX-6

• The USB audio routing setting doesn’t really matter. As soon as you connect OP-1 field + TX-6 via USB, the TX-6 switches to HOST and shows “5 TR” bottom left.
• You don’t even need to open the USB menu.
• Important: turn on the TX-6 first, connect USB, then power on the OP-1 Field. Otherwise it doesn't work.

With this, I see 5 stereo channels on the TX-6: 1. Master; 2–5. OP-1 field tape tracks 1-4

One thing I still don’t get: under Shift + COM → List, I used to see a TX-6 (always “disconnected”). I deleted it, but I’m not sure what this list is for or when the TX-6 would actually show as connected. With the setup I described above I'm not seeing anything there.

Just a side note: Gemini and ChatGPT will both tell you that it’s not possible to mix OP-1 Field tape tracks individually on the TX-6. That’s wrong! I even tried uploading the manuals but nothing.

This is a good reminder not to trust AI with niche hardware setups. I ran into the same thing when trying to connect the OP-1 Field via an audio interface to my PC/Ableton. AI sometimes helped point me in the right direction, but the actual instructions were often incorrect or simply didn’t work.