Hi 4Space:
Good question and you can find lots of discussions on this forum on many of these tapes such as Holosync.
I spent several years practicing with these tapes and found them to be quite powerful and helpful. To use these tapes is a mechanical way to push your brain to different operating levels. They are kind of like a treadmill for a runner and force your brain into deeper states and help you to unload a lot of stress and mental and emotional blockages and junk stored in your body. I think for people starting out with meditation they can be very helpful to allow you to experience deep meditative and relaxing levels. I never mixed SFQ practice with listein to these tapes SFQ, but would just do them at different times of the day, because in SFQ instead of relying on a mechanical way to push our brains we rely on a master, the universe or god.
I no longer use these tapes at all as I believe and trust in the universe/god to take my brain to the right place while practicing SFQ. I find that I am much more disciplined and thoughtful both during and after SFQ practice and no longer need the mechanical push.
Agent B