aquario mentioned out-of-phase tones and such so I thought I would add this about my own experiments with brainwave entrainment. Despite the name it is simply synching our brains to music or a beat to produce a particular effect (calmness, for example).

Using recordings of a steady tone at different frequencies, I find that 6 Hz is special to me. Five is not nor is seven. I find that fist thing in the morning, 6 Hz will dissolve my "curly toes" in about three minutes and relieve general cramping in about the same time. I am not tremor dominant but the times I have tested it, it has had a positive effect. Also, a similar effect is found around the 130 Hz area. That's as far asI have gotten.

This is pretty safe stuff with 100,000s sold to help you remodel yourself, but if epileptic be more cautious. If you want to email me I will send you an mp3 to play with. Or, if you want to get really into it, search for the shareware program "BrainWave Generator". It really does do things. Just banishing curly toes is worth a small fortune to me.