From my own extensive use of different levels of consciousness, as a Channeler and Hypnotherapist, and also as a user of the Holosync, my observation is that it starts out in the alpha, and gradually moves you into the deeper Theta, mostly, and occasionally into some Delta on certain of the CD's.
I have trained myself to know pretty much where my level is, by certain cues my body gives me, so my additional comment is that they have done a remarkable job on these paraliminals of moving you into exactly the right level of mind at the right time. I may be a newbie as far as the paraliminals are concerned, but I am finding them highly effective in my life.
Cheers,
Unis 
