Q:

Is it possible to record higher frequencies using multiple microphones sampling in lockstep?

I have only a basic understanding of audio, so this may be somewhat naive, but is it theoretically possible to record frequencies above what microphone allows by using multiple devices sampling in lockstep, i.e. assigning phases of desired frequency to each? Or is there a physical limit, like for example waves above some frequency not causing the membrane to vibrate?

A:

frequencies above what microphone allows

Microphones have a frequency response curve. This is a random example: 

The exact shape of the diagram is different for each microphone, but they all have one thing in common: the response will be as close to flat as possible in the range we're usually interested in (20 Hz- 20 kHz for full-range audio microphones), and will roll off outside that range. 
So there's no hard cutoff, but as the frequency gets higher, the microphone's output signal becomes weaker. This is due to the membrane, but also the electronics inside the microphone. Outside the frequency range shown in the graph, this roll-off continues, so pretty soon, the mic becomes really insensitive. 
Any sampling occurs at the microphone output, so it has no way to avoid this response. 
It may be easier to get a specialized microphone for ultrasonic applications, or you could switch to a laser microphone, skipping the vibration->electric signal step altogether. 

