That concept is based on Lessac's notion of the "Y-buzz" sensation. Here is a 2007 study by Barrichelo and Behlau that looked at the perceptual salience of that highly resonant sound/sensation, as opposed to "normal" production by subjects of the acoustically similar [i] sound (as in the word, "me,' for example.) The unique, therapeutically created Y-buzz vowel felt sense is the model for our work. The learner's ability to produce the Y-buzz is almost entirely body-based, not auditory. In that way, the learner can produce it without having to "go through" the possibly "defective" [i] vowel in his or her current interlanguage phonology. (See earlier post on "changing the channel.")
Need to put a little more "buzz" in your teaching?