In my relentless reading on Karate and all of its facets, I find that Kata is very often compared to many other Arts, and the main analogy is the Yin and Yang, soft and strong, calm and powerful, similar to that of a great musical composition. Robust and exuding intense energy at points, and then tranquil and fluid in others.
In my own kata I make the mistake of leaning on the power side of the Kata, often making it look abrupt and stiff – lacking the spaces of fluid, calmer transitions and movements after points of high intensity.
Mas Oyama, in his three principles of Kata, referred to this as 力の強弱 Chikara no Kyōjaku: The Relative Force of Power, where he suggested the power of a technique derives from the proper balance between strength and relaxation. Try to keep up the strength component (as I often do) and your kata becomes one dimensional, your tempo is off and your energy quickly drains.
Consider this thought on Kata performance by Kasuya Hitoshi Sensei: “During Kata performance do not put out too much power, do not be too relaxed. Even though your actions may be violent, your mind should be controlled, full of spirit (TSUSHIN). Your mind should be enriched, without any idle thoughts (ZANSHIN).”
Now consider this line by J James from the Shotokan Way regarding Jion Kata: “Jion is a Kata of calm power and smooth transitions.”
If we consider kata a performance such as a musical composition rather than a set of techniques, we have to pay as much attention to the spaces between the notes as much as the notes themselves. The points of Kiai are to exhibit the intense culmination of Mind, Body and Spirit, while the other components are crisp and yet fluid. Transitions from the subtle notes (techniques) to the crescendos (Kiai) really tell the tale.
A strong punch is important, but how you get there is paramount.