Vocal scientists are very wary of visualization-based techniques because the metaphors are usually superficial and offer no common point of reference between the teacher and the student. I am not against metaphors at all, because I find that many students are very visual learners and the metaphor based on physiological substance is often the very aid they require to make a leap forward. The Metaphor of the Flagpole and the Flag has been particularly helpful in helping the student make sense of sensory feedback.
The sensations that we refer to as chest voice and head voice in my opinion can be reduced, respectively, to a sensation of grounding in the chest (I shy away from the term anchor. More on this later), and the sensation we often articulate as vibrant in the mask. These terms are often conceived as extremes from which a happy medium must be achieved (i.e. a little less chest voice yield more head voice). This kind of one dimensional continuum is inaccurate and causes misunderstandings with respect to sensory feedback. In terms of actual function, it might be better to conceived of a double-continuum with interrelating parts. The sensations of grounding in the chest is based on a continuum of fold depth and tensile stress directly proportional to the combined activity of the Internal Thyro-Arytenoid muscles (TA or Vocalis) and the Crico-Thyroid muscles. The most efficient fold posture for a given pitch depends on a specific relationship between these two muscle groups. Once the ideal (or near ideal) fold posture has been accomplished, then fold closure must also be near ideal in order to maintain the desired pitch. Too loose a closure would accelerate the open cycle and could cause a rise in pitch. To maintain pitch, the fold depth might change. All of this would be relatively inefficient. Yet the change might be minor. Likewise, too tight a closure would cause a lessening of the fold depth in order to maintain desired pitch. In the best case scenario however maintaining the proper fold depth (i.e. adequate chest voice sensation, i.e. grounding) would facilitate a closure strategy whereby the folds would touch just enough to accomplish full closure during the close cycle (inertial reactance considered as part of the closure mechanism). In such a case, the fold cover would not be squeezed against the body of the fold and would be more easily set into oscillation by a relatively small amount of sub-glottal pressure.
It is my understanding that this easy vibration of the fold cover (when phonation is not pressed) induces the sensation of mask vibration that we associate with head voice. As the flagpole is of necessity for the correct oscillation of the flag by the wind, so is the appropriate sensation of the chest voice necessary for the free vibration of the gently adducted fold cover, the sensation associated with head/mask vibrations.
The correct balance of the TA and CT is not a given. Some singers have a natural coordination on many notes in their range, but probably all singers will have to learn to calibrate this muscular coordination for certain difficult notes in their voices. This part is the training that must be accomplished and in the beginning it can feel effortful. When the proper chest voice mechanism has been accomplished for the given pitch (i.e. the balance between TA and CT activity), then the easier phonation becomes possible. Finding such a balance on every note of the singer’s usable range is the daily work that every singer must do.
In a sense, the quality of ease that we hear (i.e. the fold-cover vibration) is what we identify as head-voice content. But a true head voice is not possible without the chest grounding (i.e. the muscular grounding that yields the proper fold depth). The chest grounding is a stabilizing factor that allows for easy vibration of the fold cover.