Ok, here is an unusual suggestion: Ravel s Bolero.

https://youtu.be/r30D3SW4OVw

Before you leave disgusted or mocking, hear me out:

15 mins of repeating the exact same series of notes. Only harder, louder, stronger, all the way to an unbearable crescendo.

She, standing behind you, hitting in the same sequence, at the same rhythm, totally synchronized with Ravel's motif. Music very loud, to cover your screams.

Starting mild, slowly increasing intensity, harder with every iteration of the musical phrase, exploding in a final crescendo of unbearable pain.

Every sequence of notes inexorably following the previous one.

Every sequence of Her strikes inexorably following the previous one, identical, unstoppable...only harder.

Hypnotic for both giver and receiver.

Someday perhaps...I can only dream...

My 2 cents.