I've explained on a number of occasions that the development of energy in the enneagram depends in large part on the development of the octaves of energy within the individual centers.
Each center encompasses its own octave. The extent to which each center develops within its own octave has a great deal to do with the possibilities an individual can express. This iteration of notes within subordinate octaves is precisely what gives us Gurdjieff's 27 types.
More importantly, perhaps, we can see that if an individual developed in even one center to the degree of Sol, La, or Si, this would produce a yogi of extraordinary powers, one who stood apart from other men.
This would not, however, be enough of itself, because it's only with a balanced development of each subordinate octave that the kind of stable inner evolution Gurdjieff taught can take place.
Jeanne de Salzmann understood this, and explains it in some detail in section 86 of The Reality of Being:
"In order to provoke a stop, suffering is necessary so that a third force can appear. Then the attention becomes a voluntary — I wish not to be taken, I wish to remain free. at this very moment I feel I must have the freedom to be. I experience a will for freedom. The degree of this will of the attention produces an opening of my body to a finer energy. Everything depends on this opening. I need to feel the energy in my mind and in my body simultaneously with the same force. My attention needs to last and not diminish."
" All the centers are involved. If one reaches fa, it can draw the others toward fa. all the centers must be in front of the interval for the intensity of vibration to increase. The relation between the centers is the shock necessary to pass the interval, which will never be passed without it. In our working on this relation, a force appears, and we then feel a vibration that opens the door to a different level." (The Reality of Being, page 185.)
In this section, she is speaking specifically of this development of the subordinate octaves on the right side of the enneagram, each one of which ought to develop to the note fa in order for all three of them to be able to pass to sol on the left side. This is a significant part of what harmonious development is all about. Significantly, she associates this particular action with a certain kind of will — that is to say, power, which is exactly what the note fa represents in its essence.
Perhaps more interesting, she goes on to explain that this level of development constitutes a new level of Being- exactly as it should, given the meaning of the note Sol relative to the actual forces, or influences, affecting each note, as detailed by the Names of God and their relationship to the diagram. The note Sol, after all, "means" Being. It represents the moment at which real "I" is formed.
Here we come to the crux of the matter, because at this point she advises us as follows:
"In proceeding further with the octave, the question of the second conscious shock can appear only when I have been consciously present for a sufficiently long time. In this effort of Presence, my feeling warms up and is transformed. It purifies itself, and my emotions become positive." (ibid.) (Italics here are mine.)
Here she specifically indicates that the next step- the note la- is one of purification, exactly as the diagram must read based on the iteration of influences at each note.
The need to understand the diagram as an abstract of inner relationships and inner movement is, of course, essential—as is the need to understand that these relationships are not linear and do not by default follow the traditional channels and paths as shown in yoga, tai chi, and other practices. Only the enneagram provides an accurate, if two dimesional, model of the way inner and higher energies actually relate to one another.
One final note. De Salzmann repeatedly urged us to prepare ourselves for the arrival of higher influences. The word influence means, quite exactly, that which flows into. She was, in fact, using the word in exactly the same manner and for the same reasons that Swedenborg used it three centuries ago—to indicate the inward flow of the divine substances of Love, which are the animating force that creates all matter, and gives birth to life. I might add, there is only one way of understanding these forces; both their presence and action is agreed on when they are available. Anyone who argues about it does not have a right understanding.
Sensing and understanding these influences, or inflows, of the divine will help to better understand the diagram from a practical perspective.
It's possible to understand this diagram with a number of different layers superimposed upon it, each one of which has a meaning and relationship to the centers; and in some versions of the diagram, the centers fall in different positions, for reasons too complex to explain here. The point is that because the diagram is always in motion, it contains within itself a flexibility that allows a continuous, flowing interpretive ability.
May your soul be filled with light.