Delta brainwaves are slow, loud brainwaves (low frequency and deeply penetrating, like a drum beat). They are generated in deepest meditation and dreamless sleep. Delta waves suspend external awareness and are the source of empathy. Healing and regeneration are stimulated in this state, and that is why deep restorative sleep is so essential to the healing process.
A study published in Electroencephalography and Clinical Neurophysiology by Paul Williams and Michael West in 1975 examined the brainwave states of people experienced in meditation while using photic stimulation, and another study by Leonard, Telch, and Harrington in 1999 examined the successful use of brainwave entrainment techniques for attaining meditative states in subjects.
Passively listening to binaural beats may not spontaneously propel you into an altered state of consciousness. One's subjective experience in response to binaural-beat stimulation may also be influenced by a number of mediating factors. For example, the willingness and ability of the listener to relax and focus attention may contribute to binaural-beat effectiveness in inducing state changes. "Ultradian rhythms in the nervous system are characterized by periodic changes in arousal and states of consciousness (Rossi, 1986).

Because of the way they are created, there may be a positive benefit from listening to binaural beats without considering the brainwave entrainment aspect, but I haven’t seen any research on that. I first discovered brainwave entrainment through binaural beats about 10 years ago now, but they didn’t do anything for me. So I’ve never been a regular user of them. I believe isochronic tones are a more effective way to produce hemispheric synchronisation because they produce a much stronger response in the brain
In the average person, the activity of one brain hemisphere is dominant over the other, called brain lateralization. This hemispheric imbalance leads us to experience the world in a black and white way, perceiving separation over connectedness. When brainwave entrainment is used to synchronize brainwave activity in both hemispheres simultaneously, a person can more easily integrate information from all parts of the brain and solve problems with greater intelligence and sensitivity.
Binaural beats are dual tones, each one slightly different from the other. You hear one tone in each ear and your brain responds by creating a tone to reconcile the difference between the two. Isochronic tones are single tones. The variation in pattern here is brought in by interspersing silence between the sound, which means that your isochronic tone does not have a continuous sound but tones broken up by silences. Studies show that isochronic tones have far more contrast than binaural beats because of the silence and sound pattern. This sharp contrast evokes a faster impact from your brain, prompting it to match the frequency more quickly. Also, isochronic tones are found to be stronger stimulants to the brain.
Synchronized brain waves have long been associated with meditative and hypnogogic states, and audio with embedded binaural beats has the ability to induce and improve such states of consciousness. The reason for this is physiological. Each ear is "hardwired" (so to speak) to both hemispheres of the brain (Rosenzweig, 1961). Each hemisphere has its own olivary nucleus (sound-processing center) which receives signals from each ear. In keeping with this physiological structure, when a binaural beat is perceived there are actually two standing waves of equal amplitude and frequency present, one in each hemisphere. So, there are two separate standing waves entraining portions of each hemisphere to the same frequency. The binaural beats appear to contribute to the hemispheric synchronization evidenced in meditative and hypnogogic states of consciousness. Brain function is also enhanced through the increase of cross-collosal communication between the left and right hemispheres of the brain.
Brainwave entrainment music can be used almost anywhere and anytime, making this mood and self-improvement method versatile and flexible enough to do at work, while traveling, or at other times during the day. When used in the workplace during short rest periods, brainwave entrainment techniques can enhance concentration, communication, and work productivity.
When the track is over you can continue to meditate without the help of the entrainment track.  When you are ready to get up, thank your Higher Self for the experience and remove your blindfold, keeping your eyes closed.  Stay seated with your eyes closed for a few moments, then slowly open them and take a moment to let your eyes adjust to your environment’s light. 
Stress can either be perceived as feeling good/positive or bad/negative depending on the context, and the body reacts differently to both kinds. However, where the body isn’t so clever is distinguishing between very serious threats (like being robbed or starved) and events that are stressful but not actually life-threatening. Unfortunately, whether a problem is very serious or not, the body usually has no way of knowing the difference− — anything that causes you to worry, anticipate, regret, overthink or panic can send your stress levels through the roof.
Alpha is the resting state for the brain; it is “The Power Of Now”, being here in the present. The Alpha state is the relaxed state of consciousness essential to stress reduction. It is intensely pleasurable: you are awake but relaxed and not processing much information, with a sort of floating feeling. According to Alpha researcher Dr. Joe Kamiya, the Alpha state is “something like letting go of anxieties”.
That is generally where the science ends and the pseudoscience begins. A number of companies and individuals have then extrapolated from the phenomenon of entrainment to claim that altering the brain waves changes the actual functioning of the brain. There is no theoretical or empirical basis for this, however. Entrainment is a temporary effect on the synchronization of neuronal firing – it does not improve or increase brain functioning, it does not change the hardwiring, nor does it cure any neurological disorder. There is no compelling evidence for any effect beyond the period of entrainment itself.
The aim of this study is to identify tendencies in the effectiveness of relaxing audio stimuli that could be verified through further focused experiments. A series of brainwave entrainment (BWE) techniques for inducing relaxation will be presented consisting of different binaural phenomena (BP). The BP will derive from the binaural sine wave beat, widely acknowledged in rhythmic BWE... [Show full abstract]
“In order to get into a flow state, you have to calm a part of the brain, the posterior cingulate cortex, which is the source of what brain scientists call the default state, which is the non-focused state,” says Harris. “At any rate, it turns out that Holosync [binaural beats], when you listen to it, [calms that part of the brain] and so does traditional meditation. It’s just Holosync does it faster and more easily and more effortlessly. It turns down the posterior cingulate cortex and it enhances the other part of the brain that, when it’s enhanced, you can easily go into a flow state.”
With digital upgrades, Berger’s machine is still in use today, known as an electroencephalography machine, or EEG. Berger used his machine to study the brains of psychologically normal and abnormal people and discovered the first brainwave, called the alpha wave and also known as the Berger wave, along with the faster beta wave, which he observed suppressing the alpha wave when subjects opened their closed eyes. 

Your brainwave activity during sleep is largely distinct from your brain activity when you’re awake. (REM sleep is one exception to this—during REM, your brain is active in ways very much like when you’re awake.) During non-REM sleep, the slower, lower frequency theta and delta waves dominate, compared to the alpha and beta waves that are prominent when you’re alert and active.
Now I’m in the market for two extra tracks to have some variety. I have narrowed it down to a couple of ones including muscle relaxation which is theta and delta. I have a hard time relaxing my body. The last time my muscles where relaxed was after intensely cleaning my stove. I don’t want to clean every time I want to relax, even though my house will be spotless ;).
Beta brainwaves are typically those we experience when we are wide awake and full of energy. You can think of this frequency as the equivalent of taking stimulants like caffeine, Adderall, or various nootropics. The Beta frequency is good for generating a concentrated, focused, and analytical mind. In fact, the brainwave you probably possess while reading this is of the Beta frequency.
Many people experienced in using alpha brainwave entrainment report that the state of mind associated with alpha waves is a time when they feel most consciously connected to their subconscious mind. The intense experience of hypnagogic sleep, reported by some people as a feeling of being awake and asleep at the same time, is also associated with alpha brainwaves.
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Participants in the included studies were children and adults, either healthy or with conditions such as learning disabilities, attention deficit hyperactivity disorder, migraine, stress, anxiety and myofascial pain. Interventions included single, alternating, ascending or descending frequencies of photic or auditory stimulation or audiovisual entrainment selected either by the participant or by the investigator. Nearly half the studies used single sessions and the rest used multiple sessions ranging from nine to 100. Length of session varied from 0.5 seconds to 60 minutes. Frequency of session varied from twice daily to weekly. Outcomes reported in the review included cognition (including verbal skills, performance skills, attention, memory and overall intelligence/achievement), short- and long-term stress, pain, headache/migraine, mood, behavioural problems and premenstrual syndrome (PMS).