"While listening, your heart rate gradually comes to match that beat. It is important that the song is eight minutes long because it takes about five minutes for this process, known as entrainment, to occur. The fall in heart rate also leads to a fall in blood pressure.
The harmonic intervals - or gaps between notes - have been chosen to create a feeling of euphoria and comfort. And there is no repeating melody, which allows your brain to completely switch off because you are no longer trying to predict what is coming next.
Instead, there are random chimes, which helps to induce a deeper sense of relaxation. The final element is the low, whooshing sounds and hums that are like buddhist chants. High tones stimulate but these low tones put you in a trance-like state."