Like I said, the same reverberation effect can be achieved via natural means, e.g. walls of a concert hall built in a peculiar way and wisely adjusted ceilings. That particular performance was taking place on a Fender company birthday, so that everyone playing there that day was put in the same conditions (specific hall+combo amplifier, with no specially assigned concert hall for Alexey). Just listen to the sound instead of trying to pose music as sport

Or did you actually think that opera singers are really able to cover a room sized like small stadium without the help of walls and ceiling?