By simultaneously combining the sounds of two didgeridoos, a desired state of consciousness can be induced in the listener. For example, when one didgeridoo is played in the key of Bb (fundamental frequency of 58 Hz) and a second didgeridoo is played in the key of C (65 Hz), the difference between the frequencies is manifested as a subtle pulsing (in this case 7 Hz). The listener’s dominant brainwave state will sync with this pulsation in a frequency-following response known as brainwave entrainment.
Exercise can be an effective component of a stress management program for many individuals and should be recommended to help those who are dealing with acute, acute episodic, or chronic stress. An advantage of incorporating exercise into a stress management program compared with other stress management techniques is the well-documented physical and psychological health benefits of exercise. However, it is important to remember that exercise is only one component of a stress management program, and there might be situations that require assistance beyond the expertise of a fitness professional, especially in working with individuals who are experiencing acute episodic or chronic stress. Although exercise might be effective in helping an individual feel calmer who is dealing with these types of stress, it will not solve the problem of major chronic or regular stressors. It may be necessary to refer these individuals to resources who can help them to address their stressors, such as a psychologist or other health care providers.
Gamma brainwaves possess the highest frequency we know of. In this state, our brainwaves are so harmonious that many people report feeling elevated states of consciousness, even spiritual experiences. This frequency is often experienced by monks, nuns, yogis, and experienced meditators. Gamma frequencies also enhance memory, awareness, and mental processing.
Theta waves have another interesting characteristic. The Earth has a measurable resonance of 7.83 hertz known as the Schumann resonance. Because the Schumann resonance is a constant background frequency surrounding all life, it may play a special role in biological activity. The Schumann resonance frequency falls within the range of theta brainwaves and may have something to do with why these brainwave frequencies are so powerful. 
Neural oscillations are rhythmic or repetitive electrochemical activity in the brain and central nervous system. Such oscillations can be characterized by their frequency, amplitude and phase. Neural tissue can generate oscillatory activity driven by mechanisms within individual neurons, as well as by interactions between them. They may also adjust frequency to synchronize with the periodic vibration of external acoustic or visual stimuli.[3]