4K fps? Impossibly high? Not at all. There are consumer compact cameras and even smartphone sensors that can hit 1K fps [1] -- and those are not even specialist high speed cameras.
Specialist cameras hit 4k fps at second gear, and can go as high as million fps (and even trillion fps [2])!
Besides, this is about reproducing music frequencies, whereas the most probable target for this technology is eavesdropping, not as a replacement for Neumann U87 -- and for that you need way less range.