Walpurgis Delay / Momentary

[Tune Tone]

Hey
I jsut ran into this sick momentary delay which sounds really really cool.

Walpurgis Delay

Any idea what schematic this guy has follown ?
I would in general be really interested in delay projects that give this psych and silly sounds liek Clari Not for example or this one in the photo which looks really really cool. Like the Boss DD3 hold function..
stuff like these.
any advice is welcome !
thanks!