We actually are composed of energy. After all, E=mc^2. But when you get down to it, all that we know of subatomic particles leads to the conclusion is that everything that exists is made of nothing at all. The free conversion of mass to energy and back creates massive problems assigning the "reality" of a thing. The only thing that makes it real is that we perceive it to be real. When we try to understand the underlying nature of the structure of matter/space/energy it becomes a blurry mess. Observing how it interacts is one thing. Understanding what "it" is, is something else.
Along the vast stretch of natural harmonics, I'd find it strange that a single frequency can have that much impact. Everyone's own natural harmonics based on their size, moisture content, bone density, lung capacity, are different and will understandably have their own favorite sounds and natural scales. Western music in Europe has a different flavor that Chinese music of the same era. They use different scales to evoke a variety of moods.
In other words, not everyone wants to chant "OM" at the same frequency.