1

No root needed, HTC One A9 records calls perfectly in two sides, just install Boldbeast Recorder and go.
Please use these settings to record calls:

- Record Mode: 1 or 5
- Tune Audio Effect: No
- Tune Audio Route: Group3

2

HTC U11: HTC U11 Call Recorder
HTC 10: HTC 10 Call Recorder
HTC One A9: HTC One A9 Call Recorder
HTC One M9: HTC One M9 Call Recorder
HTC One M8: HTC One M8 Call Recorder
HTC One M7: HTC One M7 Call Recorder
HTC One E9: HTC One E9 Call Recorder
HTC One E8: HTC One E8 Call Recorder