Good sousho is written with changes in rhythm but without pauses, unless one is introduced intuitively as an accent. The calligrapher unifies with the rhythms of his mind and loses himself in his soul. Moreover, the mind needs to precede what the brush creates. Any hesitation is obvious, making the sakuhin (作品, final work) look unnatural and forced. For this reason, calligraphy should be created from start to end, without distractions.
Sousho may appear random and completely abstract; however there are rules to it. Basically, the left-hand radical of the given kanji is simplified and the calligrapher emphasizes its right-hand side. Due to the complexity of kanji, there are guides for simplifying radicals and compounds. Even a tiny error may mislead the reader, suggesting a different kanji, and therefore a different meaning. Then again, since calligraphy is an art, some features are magnified and other simplified, which makes reading sousho extremely challenging. Writing it takes intense concentration and focus. Reading it requires a vast knowledge of sho.
Today, cursive script is understood to be any style where the strokes are executed swiftly (or they appear that way) and they tend to “round off” and “simplify” the structure of the given character.
The prevailing rules of sousho consist of: not lifting the tip of the brush too often to maintain contact with the paper while writing a character (or even a whole verse), and simplifying characters by merging or omitting certain strokes. Merging characters is called renmentai (連綿体, lit. “unbroken line”), yet it does not necessarily suggest that the line has to be physically connected. The connection can be “suggestive” where we can almost see the line on the paper, but in fact it does not exist. The calligrapher writes in a way that when he lifts the brush, he is writing a line in the air and when the tuft lands on the sheet once more the space between the kanji creates an illusion of an unbroken line. This is similar to dance, where the gestures and rhythm are an extension of the form. Naturally, renmentai can be literally one long ribbon of ink, merging up to dozens of characters. Renmentai is essential to the Japanese calligraphy style called kana (かな).
In western terms, sousho is comparable to a jam session of absolutely brilliant musicians. It has everything the soul needs: the tempo, the passion, the melody and rhythm, both strong and soft accents, surprise, and most importantly; the ingenuity and charm of natural improvisation.