and then suddenly relaxes the tension with some kind of humor or light touch, before starting to build again?M

YES!

(mild spoiler)

Norman Bates is sinking the car in the swamp, watching it, WE are watching it as the car goes down and the mud bubbles up bloop...bloop...bloop...

And it stops.

The car stops sinking.

Norman bites his thumb nail, a slight sign of tension, we start speculating WHAT IF IT DOESN'T SINK? WHAT WILL HE DO? WHAT IF...

And at that VERY moment, the car starts to sink again, below the surface, and Anthony Perkins sort of smiles...but doesn't...it's very, very subtle.

HITCHCOCK! YOU PLAY WITH US!!

Loved it. Gawd, so many things like that.