In 1973, biophysicist Dr. Gerald Oster published a famous article in Scientific American titled “Auditory Beats in the Brain”, which found that when two pure tones of varying frequencies were combined, a third rhythmic beat was created which he called binaural or monaural beats. According to Oster, monaural beats occur when two tones are combined and sent through a loudspeaker, while binaural beats occur when stereo headphones are used to deliver each tone separately to each ear. Oster concluded that monaural beats were a more effective form of brainwave entrainment.
So, what we’re doing is combining these two parts, the awakening of complete stillness and deep relaxation with the rhythmic sounds, and embedding all frequencies within the music from right at the upper limits of human hearing to the lower limits. There is multi-level entrainment within Journey—I’ve layered in everything I know about audio brainwave entrainment into this track. 
Brainwave Entrainment is the process of synchronizing the brain to specific frequencies and patterns embedded in audio tracks. These frequencies correlate to specific emotions, feelings, and even energy levels. Using nothing more than sound, Brainwave Entrainment can enhance creativity, change moods, and even alter behavior like sleep and energy levels.
... Audio visual stimulation effects people on two levels: Budzynski (2001) reports significant improvement of mental capabilities after AVS in 75-year old male. Cruceanu and Rotarescu (2013) proved that the exposure to 30-minutes of audio-visual stimulation with the frequency of 10,2 Hz significantly improves cognitive skills. Based on their research, authors claim that people need to be exposed to AVS at least for 20 minutes in order to achieve positive effects. ...

It cannot be any wonder then that we are almost desperate to find some sign, some indication that meditation and brainwave entrainment is having tangible, definable effects. We seize on these odd little experiences like ‘flushing of the face’ or ‘seeing spirals of color’ when our eyes are closed, hoping these are signs suggesting the elusive relief we’ve been after is finally within our grasp. We ask others to validate our experiences so that we can reassure ourselves we’re on the right track at last.
As strange as it may sound, vocal toning is a special technique that reduces the stress hormones adrenaline and cortisol. Try sneaking off to a quiet place to spend a few minutes toning before a meeting with your boss and see how much more relaxed and focused you feel. It works by exercising the tiny muscles of the inner ear that help you detect the higher frequencies of human speech that impart emotion and tell you what someone is really trying to say. Not only will you feel more relaxed in that meeting, you’ll also be better able to understand what he’s trying to communicate.
2. The other thing you cannot afford to do is evaluate whether or not a technique is having an effect based upon having (or not having) any of those superficial, irrelevant, distracting phenomena discussed above, like face flushing, seeing light swirls, having sensations of this, that or the other thing, etc. Those kinds of phenomena will just lead you down the wrong path and steer you away from the true benefits of meditation. If you’ve already fallen into the trap of this sort of conditioning, using something like the Release Technique, the Sedona Method, or even EFT can be helpful in breaking established conditioned associations.

♥ When I learned about Binaural beats and found out how you can influence your state of mind, I utilized them for most of my college studies. I play 16Hz Beta waves behind my favorite study music. I've been using them for 3 years now and they help me stay focused longer. Just make sure you have quality headphones that can reproduce the frequencies accurately. 2Hz does make a difference with an EQ.
A therapy that slows brainwave activity, helping to produce low-frequency waves, is likely to aid relaxation and sleep. But it’s not only lowering brainwave frequency that binaural beats may offer to sleep and relaxation. A small study (19 people) has found that exposure to binaural beats is associated with changes to three hormones important to sleep and well being:
The phenomena of brainwave entrainment was first described in the scientific literature in 1973 by Gerald Oster in results published in an article in Scientific American entitled, “Auditory Beats in the Brain”. He showed that a specific brainwave could be induced when a person heard two separate, but closely related, sound frequencies, one in each ear. He discovered that when the frequencies heard by each ear differed by about 10 hertz, the brainwave pattern of the person hearing the sound would synchronize to the difference between the two frequencies. For example, if the person heard a 410 hertz sound in one ear and a 400 hertz sound in the other ear, their brainwaves would stabilize at the difference between the two, or 10 hertz. This technique is called binaural beats, and it is a fundamental principle of brainwave entrainment methods.

  That said, you achieve the best results when you listen to the tones in a relaxed, quiet environment, investing your complete attention to the tones and the effect they have on your inner self. Experts recommend that even isochronic tones be heard via headphones to cut out distractions from external noises. The best thing to do is give it your entire, undivided attention, so that you can experience the outcomes quickly and easily.

Theta waves are associated with ➤ Increased sense of inner peace and emotional stability ➤ Deep relaxation ➤ Improved memory ➤ Heightened intuition and inspiration ➤ Calms the chatter of your mind ➤ Increased psychic abilities and sense of spiritual connection ➤ Speed healing, improved physical healing ➤ More restful sleep ➤ Release beneficial hormones related to health and longevity ➤ Reduce mental fatigue ➤ Reduction of anxiety and stress
Transparent Corp's Research Area is arguably the most comprehensive resource for collated brainwave entrainment research.   Update: the main research area on Transparent Corp's website is currently being updated, so it is offline.  However, you can still access their peer-reviewed research paper as a PDF here: “A Comprehensive Review of the Psychological Effects of Brainwave Entrainment“.
Slightly higher-frequency entrainment can lead to hyper suggestive states of consciousness. Still higher-frequency EEG states are associated with alert and focused mental activity needed for the optimal performance of many tasks. Perceived reality changes depending on the state of consciousness of the perceiver (Tart, 1975). Some states of consciousness provide limited views of reality, while others provide an expanded awareness of reality. For the most part, states of consciousness change in response to the ever-changing internal environment and surrounding stimulation. For example, states of consciousness are subject to influences like drugs and circadian and ultradian rhythms (Rossi, 1986; Shannahoff-Khalsa, 1991; Webb & Dube, 1981). Specific states of consciousness can also be learned as adaptive behaviors to demanding circumstances (Green and Green, 1986).  
These select frequencies and tones reduce the brain's filtering effect and allows consciousness to be set free. Each recording includes binaural beats, monaural beats, isochronic tones and other sound patterns, combined to deliver a range of delta, theta and alpha rhythms that draw your brain into hypnagogia, the transitional state between wakefulness and sleep.
Making time for connecting with the people around you, spending time outside and doing things you love with family, friends and your spouse are all stress relievers that are good for your health in many ways. Social connection is tied to longevity, since it helps people feel like they’re a part of something larger than themselves and helps give them perspective. Being outdoors has some similar effects, reminding people that they’re one piece of a much larger universe, lifting their moods and making it easier to get good sleep. (12)
Whenever we become very relaxed and the usual chatter of the mind slows down a little bit, if we remain aware and do not slip into sleep or unconsciousness, we begin to perceive things that we had not noticed before. This is slightly different than the issue of “expectations” discussed previously, although a relationship to them can develop which will be discussed below. These have to do with the fact that in our typical state of consciousness our mind is racing so fast and so loud, and our body is so engaged with activity and physical tension, that we are unaware of some subtle perceptions that are there all the while, but which get buried beneath all the physical and mental noise.

Everyone experiences stress, and not all stress is bad. Individuals who experience acute episodic or chronic stress are at increased risk for developing stress-related health problems. Research supports the idea that exercise can improve the way the body handles stress, and it can provide a time-out from stressors. Exercise programs meeting the current recommendations for health included within a stress management program can be effective in stress reduction. However, it is important to consider the client’s stressors and physical activity barriers, activities the client will enjoy, and the exercise setting. Prescribing exercise for clients seeking stress management is recommended, but fitness professionals should recognize that some clients will need additional assistance for managing stress and major life stressors.

Brainwave entrainment is a simple concept. It’s simply causing your brainwave frequency to align with some intended frequency in order to produce some intended result. It’s a way of modulating your brainwaves to resonate at a certain frequency. Being that there are certain dominant frequencies associated with different states of consciousness, this is being researched as a quick and effective way to induce states such as sleep, alertness, concentration, and even meditative and deep sleep states.
Please note: When you take one earphone out, move it as far away from your ear as possible. With some headphones you may still be able to hear the pulsating sound if the removed headphone is still fairly close to your ear; this is because your brain can still detect the frequency vibration coming from the headphone. In addition, push the earphone that’s still on your ear tightly to your ear, while moving the other earphone as far away as possible.
A popular opinion in the brainwave entrainment community is that listening to isochronic tones without music produces a much stronger effect.  However, in the study by Doherty, Cormac. “A comparison of alpha brainwave entrainment, with and without musical accompaniment” (2014),  it was concluded that brainwave entrainment was equally effective for isochronic tones, both with and without music.
Thanks for your compliment on my article. 🙂 There are some frequency lists which reference and quote some links to metabolism, but I don’t know how effective or reliable that information is. One of the good things but also a drawback of this technology is how accessible it is to use and create tracks. That makes it unattractive for big companies to invest in large-scale research because it’s hard to patent and protect any product they produce based on the research. As soon as they released the frequency data, people like me would produce free videos and cheap MP3s to utilise the research, so they wouldn’t be able to get a good return on their research investment. So to try and gain some insight into what is working for people, at the moment, we are relying upon assessing anecdotal feedback in many areas. Before buying any products/tracks for increasing metabolism, I would look for and try out free videos on YouTube first, to try and gauge how those particular tracks and frequencies work for you.

Effects on cortisol: The hormone cortisol is commonly associated with stress, and when levels are higher than usual, it can have a negative impact on the body. High levels of cortisol can lead to a range of conditions, including Cushing syndrome, menstrual cycle and female libido changes, anxiety, and depression. Dr. Giampapa noted a reduction of cortisol of up to 70-80 percent in several study participants.
In 1956, the famous neuroscientist W. Gray Walter published the results of studying thousands of test subjects using photic stimulation, showing their change in mental and emotional states. He also learned that photic stimulation not only altered brainwaves, but that these changes were occurring in areas of the brain outside of vision. In Walter’s words:
While visual entrainment is more powerful than audio alone for inducing desired brainwave states, more caution is needed when using visual methods. Between 0.3 and 3 percent of the population is susceptible to having seizures from flickering light stimulation, and for other people, flickering visual stimuli simply makes them uncomfortable. People with epilepsy have a greater chance of having a seizure from exposure to flickering light stimulation.
Controlled or pre/post studies of the effects of BWE using auditory or visual stimulation were eligible for inclusion, provided pulses of light or tone were delivered at frequencies hypothesised to have a beneficial effect or in line with a protocol addressing clinical outcomes. Studies were required to report clinical or psychological outcomes (measured using standard methods or as deemed appropriate by peer review) and to report statistical analysis. Studies of outcomes such as electroencephalogram (EEG) response or neurotransmitter levels were not eligible. Case studies were excluded.