As weird as this is to the "concerned parents and teachers" in Oklahoma, it is a basic effect of our minds and perception. There are no demons, no narcotic gateways, no pushers, and for most people, no permanent effects(*).
When the "Brain Machine" aka Sound-Light Machine (SLM) article came out in MAKE, I immediately built one. For me, it works great, and the visuals I see tend to be geometric patterns, depending on the frequency of the beats. It can be quite intense. For those who haven't seen this, apart from the silly graphics on the glasses as pictured in the article, the "brain machine" is a pair of safety glasses with LEDs, the microcontroller, and a headphone jack. The LEDs flash in synchronicity to the binaural beats, and this is what makes it so powerful -- your brain gets two very important senses stimulated the same way. Once the sequence finishes, the effect is totally over, there is no linger feeling, or "high" or demonic possession.
They used to sell audio cassettes that had binaural beat recordings. After I built the SLM, a friend showed me cassettes he had purchased a couple decades ago in Europe, but I haven't heard them to compare.
(*) The only caution I can think of is the possibility of bad effects in people susceptible to seizures. I don't know enough about that condition to know if seizures can be triggered through our hearing, but the SLM-like devices could possibly be a trigger to light-sensitive individuals.
One can find lots of related devices on the net. In no order are:
MindSpa
Procyon AVS
For helping with autism: Audio/Visual Entrainment
Seeing this video I can't help but laugh. It's the same tired Suburbanite Scare Story that D&D was in the 70's-80's, or that "satanic cults" were in the 80's.