A tuning fork emits a pure tone because there's sexual tension between the tongs. Or something. I don't know the science.
Let go of the details and think about this:
in a tuning fork, the interaction of two creates one, pure tone.
The aim of this paper was to let the two systems of proving the Calculus - standard and non standard analysis - interact and create the pure tone of how to put logical handles on infinity.
I mean, what is sexual tension if not the whisper difference between two of kind, eh? Ehhh... ;)