At the University of Cincinnati College Conservatory of Music I was discussing the topic of left-brain right-brain activity with Claire Calahan, the CCM Professor of Classical Guitar Performance. Calahan, who studied under Andres Segovia, pointed out that scientific studies have suggested that when you breath and the air flows mostly through the right nostril, then the left side of the brain is more active. And when your breathing flows mostly through the left nostril, then the right side of the brain is more active. Usually the body will naturally cycle between the two nostrils by opening one side more than the other for anywhere from 5 to 25 minutes then switching the majority of the air flow to the other.
This is an involuntary action that happens without us thinking about it. But you can change the airflow by holding your finger to one nostril to stop the air flow. After a few minutes, the other nostril takes over the majority of the air flow.
Since left-brain is more logic and right-brain is more creative, we should experiment with controlling brain activity during song writing sessions, rehearsals and performances, and see what happens.
The body needs to be tuned, just like the guitar.