Theta brainwaves are next highest in frequency above delta and are especially important for many people using brainwave entrainment and meditation because theta waves are at a threshold, forming a link between wakefulness and the subconscious mind. Theta waves bridge between our awake self and the creative and insightful understandings from below our conscious awareness, and while they are not common in awake adults, they are normative for children under 13 years old. 
Some studies have found that binaural beats can affect cognitive function positively or negatively, depending on the specific frequency that’s generated. For example, a study of long-term memory found that beta-frequency binaural beats improved memory, while theta-frequency binaural beats interfered with memory. This is something for scientists to continue to examine closely. For people who use binaural beats, it’s important to understand that different frequencies will produce different effects.

Most of all, don't feel bad if you fall asleep. Your brain is still receiving many of the benefits of entrainment while you sleep through the audio tracks. In fact, many people report better, more restful sleep when they use brainwave entrainment to help them fall asleep. However, I recommend that you do not go to sleep with your brainwave track set to repeat, as that can be too much stimulation for the brain.
Stress levels and a proper diet are closely related. When we’re overwhelmed, we often forget to eat well and resort to using sugary, fatty snack foods as a pick-me-up. Try to avoid sugary snacks and plan ahead. Fruits and vegetables are always good, and fish with high levels of omega-3 fatty acids have been shown to reduce the symptoms of stress. A tuna sandwich really is brain food.
Once you begin to experience the beneficial aspects of brainwave entrainment, you may be tempted to have these tracks playing all the time during your waking and sleeping hours. This is NOT advisable, nor is it necessary. Remember, brainwave entrainment is exercise for your brain so your brain will need to rest and integrate the new changes that your entrainment regime is creating.

Gamma waves are the fastest of the brainwave frequencies (high frequency band of brainwave activity) which signifies the highest state of focus possible. They are associated with peak concentration and the brain’s optimal frequency for cognitive functioning – the 40 Hz frequency corresponds to a Schumann resonance band and many scientists, including Nobel Laureate Sir Francis Crick believe that it may be the key to the act of cognition. The Gamma state relates to simultaneous processing of information from different brain areas; information passes very rapidly.
I call the kind of intuitions and inspirations that come when we meditate and do these kinds of practices my “marching orders.”Okay, this is what I need to do. We’re not using our brilliant linear minds here; that’s not the place wisdom comes from. The place of wisdom is, again, relaxing into these states with loving-kindness, and then all the stuff can come out, whether we are dealing with our shadow issues or dealing with our light issues—the wisdom and gifts we haven’t yet brought forth that need to be birthed.
Insomnia and PTSD for most of my life are real bears that I wrestle with every night. A brain neural-therapist (for lack of a better description) said that this kind of sound recording may help. It is not music. When I remember to play the disc, I fall asleep within the first 5-8 minutes. One day I played the disc while cleaning and I was very surprised to hear how much of the recording I never recall hearing before. That's why I know how long it takes to fall asleep.
Generally speaking, the brain will usually entrain to the strongest stimulus which would be isochronic tones over binaural beats. So when you see people add binaural beats at a different frequency to the isochronic tones, that would not produce additional brainwave entrainment at another frequency. If they are both at the same frequency I haven’t seen any research to indicate whether that would be beneficial or not, but my belief is that it would weaken the potential for entrainment. When you look at the waveform of an isochronic tone there is a distinct empty space between each beat, making it very pronounced and effective. When you add binaural beats at the same frequency it looks like this: The depth of the waveform is now half as deep and less effective. This is before the binaural beats are formed inside your head, where the waveform is hard to determine and measure. From listening to that type of combination the beats sound much less pronounced, which has to make them much less effective in terms of a brainwave entrainment stimulus, compared to isochronic tones on their own.
Binaural-beat perception originates in the inferior colliculus of the midbrain and the superior olivary complex of the brainstem, where auditory signals from each ear are integrated and precipitate electrical impulses along neural pathways through the reticular formation up the midbrain to the thalamus, auditory cortex, and other cortical regions.[6]
Brainwave entrainment is a colloquialism for such 'neural entrainment', which is a term used to denote the way in which the aggregate frequency of oscillations produced by the synchronous electrical activity in ensembles of cortical neurons can adjust to synchronize with the periodic vibration of an external stimuli, such as a sustained acoustic frequency perceived as pitch, a regularly repeating pattern of intermittent sounds, perceived as rhythm, or of a regularly rhythmically intermittent flashing light.