For one thing, there is no such thing as "duality" or "split mind". The terms come from within the perspective of mind that looks at words or ideas, instead of actuality, words that indicate or imply something that is not true. It's all conceptual.
In such a case, the mind is generating two formations:
They are simply two, mutually interdependent concepts that, together, form motivation structures, or motives, or the motivations, of personal existence.
The subjective formation exists as a reaction to the objective formation, where I will define, "formation", in a moment.
For now, let's just say that in every moment of experience, we seem to be confronted by circumstances, situations, and conditions of life -- imposed upon us by outside, inexorable and incomprehensible forces -- kind of like, "the news". Objective circumstances contain some elements that change little by little, over time, and many more elements that change a lot, from moment to moment, sometimes in repetitive cycles and sometimes as new developments. All of these functions correspond to the "objective or yang TetraSeed". Think of driving in your car: the experience consists of things that exist, that persist, that have location, and that are moving in a direction, relative to ourselves.
In every moment of experience, we are paying attention (more or less), recognizing what our circumstances are, imagining what might happen, next, and enforcing our will (intention) to control both ourselves and circumstances (by means of controlling our actions and feelings). Controlling circumstances involves, "more", "less", and the "direction" we imagine them to be going. All of these functions correspond to the "subjective or yin TetraSeed". The "yin TetraSeed" consists of attention, remembering, imagining, and intending.
Every moment of experience is the combination of "imposition from outside" (no apparent control, on our parts), and our facing that "imposition from outside," with more or less "control initiative".
So, split mind isn't split, at all. The two TetraSeeds are interactive and inter-related as a single system of experiencing. Their existence isn't even mutual; together, they form a single experience and without that mutual togetheriness, no experience. Nothing happening, nobody to experience it.
The main function of the Dual TetraSeeds is to provide contrast between perspectives -- mainly a "figure | ground" or "Foreground | Background" contrast. Contrast is a "gradient" or influence-from-being-different that causes the experience of intensity. More contrast, more intensity.
In this case, the "foreground" is the objective world and the "background" is the self. The foreground changes a lot and the background changes much less, generally, cycling within a repertoire or library of learned sensings and responses, with adaptive modifications more or less pertinent to the uniqueness of the moment. The objective world moves and changes and the subjective world recognizes it and responds. Always, there is contrast between self and world, if only through the contrast between what we remember and what we're facing, now. That's the memory function of soma -- a "subjective TetraSeed" face or facet.
What happens with memory is that it tends to fade unless refreshed. We humans have an "automatic refreshment" mechanism. That "automatic refreshment" mechanism is, imagining, of which one form of it is, thinking. Imagining is more specific than thinking, which only triggers imagining.
So, now, we have remembering and imagining, which are two facets or poles of the same thing. Remembering is "stored imagining" and imagining is opening to remembering.
Certain meditation or contemplative practices involve immobility for long periods of time and long periods of monotony. Because memory fades unless refreshed, and since such practices involve either desisting from following the stream of thoughts or desisting from imagining, the anchoring of attention in present-conditional reality (as remembered) diminishes, at which point reveries may (and commonly do) ensue. The discipline is also not to follow the imagining, but to "observe" it (which is to say, to dislodge attention from the tendency to localize on anything by catching it doing so). Taken far enough, the sense of world and body fade out and there is no world, no self, but the intuition of a kind of quality-less, location-less awareness.
Those who have worked with such disciplines to some degree of maturity recognize the futility of stopping thought by means of discipline. Thought can only be allowed to subside; otherwise, the effort to stop thought is, itself, a thought. Problem is, lines of thought often tend to be habitual and chronic, and not only not subside, but recycle.
The act of pitting one faculty ( discipline or will ) against others, ( memory and imagination ) is self-defeating.
The alternative is something quite different: to comprehensively and inclusively turn on both four-element TetraSeeds and to develop the ability to switch from element to element while maintaining continuity -- and if one is working with a specific issue, to maintain continuity of attention on that issue, until it dissolves.
One who works with this practice will likely notice that some of the elements are easier to turn on, to reach, than others. This bias reflects uneven educational development. It can be worked with. There are TetraSeed transformation procedures, for that.
What happens when both sets of four elements are turned on is that we witness the very force of life and of our very existence, in that moment. It stands are as a subject|object confrontation, "Me, facing the World" (or some particular circumstance). It's a felt thing. We feel the force of existence, the very drama of our circumstance, as a theme or drama that now seems self-explanatory.
There is no way, in my view, to describe it any better than that. For more, one must practice the TetraSeed transformation procedures, starting with the complete Set-Up, also known as The Crystal Crown procedure. The procedure involves turning on all four elements of both TetraSeeds and then integrating every TetraSeed element with every other.
With that self-other revelation comes immediate psycho-physical (somatic) changes as ones faculties, now on-line in life, synergistically combine. It's an awakening, shift of consciousness and an increase of integrity that changes how one behaves, in life. This is one definition of the term, psycho-active.
As to, "Duality", there ain't no such animal. Mind isn't dual; its apparently "separate" parts are one dynamic, living "system" (or soma), made to seem separate only because one or more of the elements of the Living-Self TetraSeed aren't comparably turned on or mutually integrated. The unconscious part seems like "other", separate from "self". "Other" may be defined, as "not immediately controllable by self".
In that sense, we are, in many ways, "other", even to ourselves -- especially on days when, "We're not ourselves."
Those days are among the best for working with TetraSeed transformation procedures.