I searched Anna Koch guitar using Google Chrome but didn't find a website for Anna Koch guitar. I found Anna Koch clarinet. Is anyone here in contact with Anna Koch and able to ask Anna, "Why did you stand in this performance?"?
Interesting strap! It appears one end is attached to the low E tuner, the other wraps around under right armpit and attaches to the bass side upper bout. I can't tell from the video how it's attached without worry of it coming off and dropping the guitar. My guess would be some kind of C-clamp against the top and back (like a violin chin rest) with double sided tape or glue for insurance.