Our hears can sense the sound waves only within a very specific band but, if you go outside that band, the waves are still there, but we can no longer sense (hear) them..
The same thing with the eyes, so our own construct of the Visible and Audible Universe is extremely limited, since most waves do not look real to us..
You say, "Isn't the opposite or inverse of division, multiplication? YES, just like the opposite or inverse of time is frequency...
1/something is a division, but in a math equation when you pass it to the other variable you still end up with a divison. For example in the energy equation e=mc2 then m=e/c2 so, in that case you are dividing c2 instead of multiplying it, but, in the t=1/f equation then, f=1/t is still a division. Is that clear now!!!
You then say: "and is illusion really the inverse of reality". YES
Illusion is indeed the false impression or appearance of something.
You further say "Time and frequency are real. Real in the definition that they are actual and have denoted properties". No Dane, I do not agree with the definition of "reality" that you are giving here!
Please tell me exactly what is the actual property of time!?
On the other hand, since you have used sound waves, you know exactly what the actual properties of those waves are.
..and you finally say, "wouldn't the opposite of reality be non-existance ( not having denoted properties)"? Well, I suppose that "to be or not be" is still the main question! LOL!!!
Would it make it easier for you then if I said that you really didn't exist here in this dimension and that you are only being projected into this physical matrix..
IMHO, you only think that you exist, because your mind tells you so.
Also, when you go to sleep, how do you know that your dream world is real or not!? Science already knows that there are very specific and different brain wave patterns associated with sleeping and many people clearly remember their dreams, specially little kids who also REALLY believe that it very real stuff what they were dreaming..
Finally, why do you think that you need to sleep every single day? and if you didn't sleep at all, it becomes immediately obvious that your ability to distinguish one reality dimension from another starts to go away! In other words, even when you are awake, you will think that you are sleeping or somewhere in between states and/or dimensions...
In conclusion, it very much possible that different frequencies are shared between dimensions, but the various constructs (stages, backgrounds) are at very distinct groups of frequencies..