Over at the Yoga Workshop webpage, Mary Taylor answers that question in a post this week:
Chanting is a very complimentary part of the asana practice as a general rule in that it is another means of drawing the mind spontaneously into a meditative state. It is also a method for focusing the mind on theory—the meaning of a chant—so that one can reflect on and question specific ideas. Of course as we chant the mind may focus on meaning for a brief period, but then the nature of chanting allows that meaning to dissolve into the background as the vibratory quality and resonance of the act of chanting (without the mind assigning meaning) has a spontaneous and deep effect on the nervous system, body and mind.
Specific to your questions about the Invocation, we usually don’t chant in situations where there are brand new students. This is because we are not trying to indoctrinate students into a “religion,” belief system or yogic lifestyle. Rather we are hoping to give students a clear and direct taste of how an asana practice can be beneficial both physically and on other levels that for different students might be open in different ways to being impacted.
Because chants have words with specific meaning, it can be quite presumptuous here in the West—or actually anywhere outside of India or a Hindu culture—to chant to a beginning group of students not knowing what their religious or cultural beliefs are. This is why we say that chanting may be problematic for some, and why we don’t shove it down the beginner’s throat. (Or more accurately out of their throat!). In certain situations where beginners may be in a class during which we choose to chant, we always say what the meaning of the chant is and also always say that students may chant along with us or simply listen.
Posted by Steve