BKS Iyengar: In many forms of yoga, teachers give instruction in beginning breathing technique simultaneously with instruction in beginning asana practice or the practice of poses. 
In Iyengar yoga, pranayama or breath control is more often taught and practiced after a student of yoga has gained a familiarity and some proficiency with practicing asanas.
So in Elizabeth’s classes, we often begin our practice of pranayama in the last class of the quarter. You may remember learning the practice of Ujjayi breathing, a sounded breathing technique sometimes begun after settling into savasana. You may have also tried the likewise sounded but louder Bhramari or bumblebee breathing technique.
Different people can experience the pranayama practices differently – sometimes as quieting or energizing or sometimes as agitating. If the practice is indeed agitating or creates any kind of strain, we should return to savasana, and seek advice from a teacher. Pranayama must not ultimately dreate disturbance. But despite the differences in any individual’s experience at any given moment, pranayama is also undertaken, in the Iyengar tradition, for very specific purposes.
In an interesting article published in the Yoga Journal, an Iyengar yoga teacher explores Mr. Iyengar’s view of pranayama and breathing in general:
[Mr.] Iyengar tells us to think of the contact of the breath against the inner lung as the connection between universal soul and individual self…The length of the retention [of the breath] varies. It should last just until the content (prana) begins to move away from the container (the lung)…Developing the ability to feel something as subtle as when the universal soul and the individual self begin to separate in the course of a breath takes regular practice and is what pranayama is all about.
But as the article explains, it is not a simple matter of making the breath do what we want to achieve this kind of awareness. Mr. Iyengar, in his characteristically poetic way says that the breath must “be enticed or cajoled, like catching a horse in a field, not by chasing after it, but by standing still with an apple in one’s hand. Nothing can be forced; receptivity is everything.”
