Gypsy Jazz Guitar - Open Strings Vibrating

[anothersixstringer]

Is that just a capo?

Yup, that's just a capo

Btw, I just discovered something and made me remember this thread. Just saw this on Facebook, haven't used it but looks like the same idea with a ...velcro wrap ?
GRUV GEAR · FretWraps String Muters / String Dampeners · MAKE LIFE GRUV

[Runepune]

I'd be more concerned if I didn't get sympathetic action from open strings