Fast answer
Inspect CC 9 on MIDI channels 1–4. In the 1.7.0 reference, those channels address tape tracks 1–4 and CC 9 values of 64 or above mute the corresponding track.
Try these checks
- Stop the sending automation and check the installed firmware against guide 1.7.0.
- Inspect messages on channels 1–4 for CC 9 values of 64 or above.
- Remove the unwanted mute automation or send CC 9 below 64 on the affected track’s channel, then test playback.
Diagnose it
Is CC 9 sent on the affected track’s MIDI channel?
Yes: Remove it or use an unmute value below 64.
No: Check track volume, recorded audio and local mute state.
What should happen
The tape track stays unmuted unless a deliberate mute message is sent.
Why this happens
The field’s track mute is a MIDI-addressable control; a generic CC track can affect the tape mixer.
If it still doesn’t work
Check the connections and settings described above. If your device behaves differently, email us with its model, firmware version and the steps you tried.
All OP-1 field fixesReferences
Sources & review
Sources reviewed: . Documentation does not replace a physical hardware test.
- OP-1 field guide — MIDI reference · Teenage Engineering · Online guide 1.7.0, MIDI reference · last checked 2026-10-03
- OP-1 field firmware downloads and release notes · Teenage Engineering · 1.7.0 release notes, 29 April 2026 · last checked 2026-10-03
Sections reviewed: Guide 1.7.0: MIDI reference, CC 9.