Binaural beat therapy works in frequencies, and each frequency falls into a certain set of brain waves which provides the patient with a certain positive result. Binaural beats of 6 Hz fall into the Theta range, which is known to produce feelings of relaxation which makes it easier for the patient to obtain a meditative state. 

Theta range waves include 6 Hz as the theta range includes all frequencies from 4 Hz to 7 Hz, the idea is that the higher in the waves you go the closer you get to the next range, sometimes you can achieve mild results of the next range in the range before.  A good example is that binaural beats 6 Hz falls into Theta range, but it is one frequency closer to the next range, namely Alpha waves. 

Binaural beats 5 Hz therapy is a precision therapy, to keep the results in a specific range the therapist has to ensure that the patient experiences the right benefits from the desired range, even if the patient is subjected to the specific range for an extended period of time. 

People who have epilepsy or any other mental disabilities should not engage in binaural beat therapy of any kind as the binaural beat therapy could result in adverse side effects.