Exercise and stress research has typically focused on aerobic exercise. There have been consistent findings that people report feeling calmer after a 20- to 30-minute bout of aerobic exercise, and the calming effect can last for several hours after exercise. Recently, there has been an increased amount of research on the role of mind-body types of exercise such as yoga or Tai Chi. Unfortunately, there is somewhat limited research on the role of resistance exercise in stress management.
Isochronic tones work just the same in delta as they do in alpha, theta and beta and they are widely used in the brainwave entrainment community to help people sleep. Like you, I’ve also seen some websites saying they don’t work in delta, but it’s a bit like the game of Chinese Whispers, where someone makes a comment and then after it gets passed around and shared a lot the message gets distorted and appears to be a fact. I don’t know of any scientific reason why they wouldn’t work in delta. I remember some people talking about this on a brainwave entrainment forum many years ago. They were saying they found isochronic tones a bit too abrupt for using to help them sleep and they preferred binaural beats, as they thought they were a more soothing sound. That was just a personal preference shared by a couple of prominent forum members at the time and some people then took that as a fact for everyone. That’s where I think that belief originated from.
Most of the tips we’ve suggested provide immediate relief, but there are also many lifestyle changes that can be more effective in the long run. The concept of “mindfulness” is a large part of meditative and somatic approaches to mental health, and has become popular in modern psychotherapy. From yoga and tai chi to meditation and Pilates, these systems of mindfulness incorporate physical and mental exercises that prevent stress from becoming a problem. Try joining a class.
... Several studies have looked at the possible effects of binaural beats within the alpha range on cognitive abilities. A significant improvement in cognitive processing, as measured by the Stroop Effect exercise, was found by a BB stimulation of 10.2 Hz frequency (Cruceanu & Rotarescu, 2013).Carter and Russell (1993)exposed 8 to 12 year old boys with learning disabilities to 8-week long 10 and 18 Hz BB stimulation sessions, and they found an improvement in Raven's progressive matrices and in a subtest of auditory sequential memory (Carter & Russell, 1993).McMurray (2006)assessed the effect of 7 and 11 Hz BB on alpha brainwave activity, working memory, and attention in healthy elderly people, who are known for experiencing gradual decrease in physiological alpha activity. The 2 minutes exposure to BB resulted in an altered electrical activity in the brain. ...
When signals of two different frequencies are presented, one to each ear, the brain detects phase differences between these signals. "Under natural circumstances a detected phase difference would provide directional information. The brain processes this anomalous information differently when these phase differences are heard with stereo headphones or speakers. A perceptual integration of the two signals takes place, producing the sensation of a third "beat" frequency. The difference between the signals waxes and wanes as the two different input frequencies mesh in and out of phase. As a result of these constantly increasing and decreasing differences, an amplitude-modulated standing wave -the binaural beat- is heard. The binaural beat is perceived as a fluctuating rhythm at the frequency of the difference between the two auditory inputs. Evidence suggests that the binaural beats are generated in the brainstem's superior olivary nucleus, the first site of contra-lateral integration in the auditory system (Oster, 1973). Studies also suggest that the frequency-following response originates from the inferior colliculus (Smith, Marsh, & Brown, 1975)" (Owens & Atwater, 1995). This activity is conducted to the cortex where it can be recorded by scalp electrodes.  
Research shows that listening to soothing music can lower blood pressure, heart rate, and anxiety. “Create a playlist of songs or nature sounds (the ocean, a bubbling brook, birds chirping), and allow your mind to focus on the different melodies, instruments, or singers in the piece,” Benninger says. You also can blow off steam by rocking out to more upbeat tunes -- or singing at the top of your lungs!
Joe:             The Journey  soundscape took a lot of work. I wanted to bring in the very best of what I knew about brainwave entrainment and to make the best brainwave entrainment product—with the best entrainment technology—that I possibly could. So, there are all sorts of things going on in Journey  to provide a sound bed to support the experience of expansiveness and also communicate elements of the heart-based work I talked about earlier. (See part I of this interview, A Guide to Transpersonal Meditation.)

Infra-Low brainwaves (also known as Slow Cortical Potentials), are thought to be the basic cortical rythms that underlie our higher brain functions. Very little is known about infra-low brainwaves. Their slow nature make them difficult to detect and accurately measure, so few studies have been done. They appear to take a major role in brain timing and network function. 

When you hit a tuning fork, tuned to a particular sound frequency such as the note B, and hold it close to the strings of a guitar, you will notice that the B string on the guitar will vibrate because it has entrained on to the same frequency of the tuning fork. Interesting enough, the other strings will not vibrate. Only the one with the same tuning as the tuning fork.
Gamma waves are the most recently discovered brainwave, a discovery made possible by digital EEG technology. Gamma is associated with the integration of information from different areas of the brain, and having a good memory is associated with having a certain baseline of 40 hertz gamma activity. Low gamma activity is associated with learning disabilities and poor memory.
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.
Infra-Low brainwaves (also known as Slow Cortical Potentials), are thought to be the basic cortical rythms that underlie our higher brain functions. Very little is known about infra-low brainwaves. Their slow nature make them difficult to detect and accurately measure, so few studies have been done. They appear to take a major role in brain timing and network function. 

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

Acupuncture has increasingly been used to treat many stress-related conditions, including psychiatric disorders, autoimmune or immunological-related diseases, infertility, anxiety, and depression. Researchers have found that acupunture treatments result in changes in the cardiovascular and immune systems, increasing protective T-cell proliferation and helping with cellular immuno-responses. (8)
Brainwave Entrainment is an assisted form of meditation using pulses of sound. Entrainment is a process of synchronizing two different beats to become harmonious. Brainwave entrainment works by pulsing a different sound in each ear to stimulate the brain into altered states of consciousness. Examples including Binaural Beats and Isochronic Tones, which are best experienced with headphones to assist with relaxation, deep sleep and focus.
In addition to the exercise prescription, other characteristics of the exercise session (e.g., group vs. individual) and the individual also are important considerations. Because of health consequences associated with stress, high-stress clients are likely to be at increased risk for cardiovascular disease and cardiovascular events during exercise. Therefore, using the preexercise screening procedures outlined and endorsed by the American College of Sports Medicine is essential (1). Monitoring exercise intensity for those looking to “blow off steam” to reduce stress might be a concern when the client has high blood pressure or other cardiovascular risk factors that further the risk increase for cardiovascular events.

Subsequently, the term 'entrainment' has been used to describe a shared tendency of many physical and biological systems to synchronize their periodicity and rhythm through interaction. This tendency has been identified as specifically pertinent to the study of sound and music generally, and acoustic rhythms specifically. The most ubiquitous and familiar examples of neuromotor entrainment to acoustic stimuli is observable in spontaneous foot or finger tapping to the rhythmic beat of a song.