Starting 0:13 in this video , how do you get the slightly muted sound (disconnected sound)?

I know for barre chords you just lift your index finger slightly to mute. But he's playing open Em and D. Also, I don't see him muting all the strings with his left hand nor is he muting with the palm. Is he just lifting up the strings with the chord (say Em, hes lifting up only the A and D string and muting them, but the other strings are still sounding?)

Can someone give me a detailed explanation of how to achieve this effect?

Thanks guys!

This muted effect has been bugging me for a while. I can't seem to figure out how to mute open chords without a chuck or palm.
it's like slightly muting the strings with your LEFT hand (if righthanded). so you lift your fingers a bit
Ibanez SA-S32 FMTL
Engl Screamer Head
Engl SS412 V60 Celestion
Engl Z5 Footswitch
Ibanez Delay
BOSS MegaDistortion
In the case of Em and D played in the video, the other strings would ring if you just lift up the fretting fingers. How does he mute all the strings in the video playing the open chords?