low quality (Score 0, Flamebait)

they are using non-linear properties of the air to downconvert from 60kHz to the audible range. in other words, the mixer is not stable or even reproducible over a range of different air conditions like humudity, pressure, temperature, etc (fog is a good example). bottom line is, while definitely a cute idea this is not for any concert or even consumer music, the quality is simply going to be way too low. but for "crowd control" and other .mil uses this might be OK. speech might be OK too, but no music, forget about music.