How to turn-off regular playback when using MIDI as output ?

I'm using my keyboard through MIDI to both input notes and listen my score (*).

When I play my score to MIDI, the regular audio playback is active. I would like to turn it off.

Anyway to configure this ?

My 2 workarounds are : 1/ Mute my PC, 2/ Mute every channel individually (I can't mute the Master).

Any better way to do this ?

(*)working at night with my headphone, so I can only wear one headphone at the time: the one connected to my keyboard.