Let's listen to a short example:
Here is the Wikipedia article on the technique used, "binaural beats" or the illusion created by hearing the difference between two tones. Here is a much better and more detailed article with examples and an examination of the claims.
My favorite wild claim is that 528 hz is the "love frequency" and also repairs your DNA! Here, give it a whirl:
Now, let me reveal the true secrets of that mysterious frequency 528 hz. It's a C. Well, ok, a slightly out of tune C, the one an octave above middle C. C5 as it is officially called, is exactly 523.251 hz (cycles per second) so 528 is slightly sharp. I can predict one sure effect from it: musicians with perfect pitch will find it a bit agonizing!
Listening to too much of this kind of music will certainly put you in some kind of trance, but I think that is simply because it is really, really boring. I believe very much that music is rather a mysterious thing, but I don't have much time for this sort of thing, that I call "musical mysticism".