I got an answer from Centerpointe about Holosync and the light and sound machines... here it is:
There are some things you should be aware of when it comes to using L/S with your Holosync soundtracks. Most important is that it's usually unwise to use two different entrainment stimuli at the same time. When you combine entrainment stimuli, there is a very strong chance that each of the stimuli will cancel each other out. It's kind of like watching two different TV shows at the same time on the same screen. Even if you have a L/S machine that syncs up with an external sound source, remember that the L/S stimulus will be generated from the loudest sounds on the external source. In the case of the Holosync program, the loudest sound is the environmental sounds, not Holosync. Using both at the same time will likely give you an interesting experience, but the basic benefits associated with each one will be limited in the long run.
Also, remember that Holosync uses low carrier frequency stimulus, while L/S is relatively limited in terms of how low the carriers will actually go. The basic reason (without making this into a long, long story), is this:
Both light and sound exist along a spectrum. With light, there is a relatively narrow band of visible light. If you try to lower the carrier frequency along the light spectrum, you quickly end up beneath the range of visible light. So with light and sound, you can't lower the carriers much without dropping into infrared (or some other form of invisible light). If you can't see the light, you can't entrain to it. However, with sound you have a much wider range (relatively speaking) in which you can "play with" carriers. You can therefore achieve much more intensive entrainment stimuli with sound than with light (although light is often a faster means of entrainment). The basic moral of this story is that while L/S machines are excellent entrainment devices, they can't offer the same kind of neural-driving feature Holosync can
One of the on-going issues in the L/S community has to do with the fact that it's possible to become immune to the long-term effects of L/S, especially if you use one session all the time. This was always a frustration for me when I was selling them. I would get calls from people about six months after buying a L/S machine saying, "Hey, my machine doesn't have any effect anymore, it's not working." It wasn't until I more thoroughly understood how the brain reacts to prolonged exposure to L/S that it made sense to me that these people were simply "outgrowing" their sessions. Later, we learned that this problem could be remedied by continuously increasing the level of stimulus (by lowering the carrier frequencies) which, in turn, continues to push the nervous system to higher levels of functioning.
We tend to see L/S devices as being best for basic relaxation and "neural recreation" whereas Holosync soundtracks are more "hard-core" personal growth tools. In the long term, you'll get the greatest benefit by using them separately.
