The holon diagram is a developmental hierarchy of skill acquisition. It is derived from the Piano Basics teachings of Dr. Kataoka. The basics are always the same regardless of the difficulty level of a piece.
The skills are built from the bottom up. Dr. Kataoka often reminded students and teachers not to put the roof on the house without a strong foundation and good walls as a metaphor for this idea.
So, at the bottom of the diagrahm is sound/intention which is obtained through listening. The student must have this idea or actually internalized sound before they are able to produce sound. The sound is the concept of the whole upon which everything else is built.
Next, “ready” is state of awareness/concentration and balance which is necessary for the other skills. Without proper balance and focus, it is not possible to play a legato melody with good tone. (It is possible to have ready and not yet be able to play legato.)
The hierarchy is a general idea and not absolute, but is none the less useful for pedagogical study. It is only a beginning to researching not just how to teach “only one point”, but how to teach the most important point. It enables a teacher to find the point that will produce the most significant benefit.
For example, it is much better to teach good tone (no tension) before teaching dynamics.
Teaching dynamics before good tone and rhythm can actually make the overall playing and development of the students ability lower. It doesn’t mean however that you absolutely never teach dynamics before everything is perfect. It is a guideline.
The idea then is that the “whole learning” which is the internalized sound and later the stage where the piece is first “memorized” is balanced with a specific one point that is the most fundamental for the student at that point in their learning.
While you may be working on tone, the student has the concept of phrase internally from listening. When they are able to physically produce tone, the phrasing will then already be there. If we skip straight to the phrasing, the awareness of the tone of each sound may be lost. So, we keep working on the most important basics in our teaching.