The name Kasen means 'Poetic Immortals' and refers to the Chinese and Japanese practice of creating ideal groups of thirty six artistic forbears. Prior to the establishment of the Basho school formalised linked verse was generally written as one hundred or fifty verse sequences. By the time of Basho's death the majority of haikai sequences were Kasen.

The structure of the Kasen reflects earlier practice in that it is based on the number of writing sheets (kaishi) needed to record the poem. The Kasen requires two folios. The six verses of the preface (jo) comprise the front of the first folio. The initial twelve verses of the development movement (ha) are written on the back of the first folio. A further twelve verses of the development movement cover the front of the second folio, and the six verses of the finale (kyu) are recorded on the back. It should be noted that some renku theorists, writing in English, distinguish between the two halves of ha, referring to the first half as 'development' and the second as 'intensification'. No such distinction is made in Japanese.

Elsewhere in Renku Reckoner the article The Seasons of Renku discusses many aspects of the way in which seasons appear and are distributed in a renku sequence. Here it is sufficient to say that in the Kasen spring and autumn predominate over summer and winter by a ratio of approximately 5:3. Spring and autumn verses each appear in clusters, typically of three, but which may extend up to five in a row. Summer and winter verses appear typically in pairs, however they may extend to a cluster of three, or be represented by a single verse at a time. Frequently a given seasonal cluster will cross the boundary between one folio face and the next.

Other than for poems begun in spring, over the course of a poem the 'major' seasons of autumn and spring will each make two distinct appearances, whereas summer or winter may be represented by a single cluster. For poems begun in spring, that season will make three separate appearances. The fixed topic of spring blossom appears twice, in the penultimate position of the first folio back [verse position #17] and as the penultimate verse of the sequence [verse position #35]. These verses are never treated as the more generic topic of flower. The positions themselves are effectively set; very rarely are they anticipated or delayed.

Moon appears as the principal topic at or around the penultimate position of the preface [verse position #5], at or around the seventh position of the first folio front [verse position #13], and at or around the penultimate position of the second folio front [verse position #29]. This latter is always autumn moon, whilst a second autumn moon verse generally appears in the preface.

Love appears as a pair of verses somewhere in the mid section of both faces dedicated to ha. Basho tended to minimise this topic whereas others of his school would give it greater extent, allowing it the full run of classic emotion inherited from medieval renga, from unconscious attraction, through consummation, to disillusionment - with all the attendant danger of descending into narrative extension.

The special compositional characteristics of hokku, wakiku, daisan and ageku were central to the technical development of the Basho school and are honoured by contemporary writers of Kasen renku. Elsewhere in Renku Reckoner the article Beginnings and Endings examines these verses in detail. Similarly the article A Dynamic Pattern explores the meaning of the expression jo-ha-kyu.

Though he is known as the father of haiku the Kasen renku and haibun [mixed poetry and prose] were Matsuo Basho's preferred vehicles for expression. It therefore comes as no surprise that the Kasen is rather good.

Given the level of misinformation and misunderstanding surrounding renku in the English speaking world, particularly the fallacy that it espouses the perpetual search for novelty, it is worth dwelling briefly on some of the salient features of the Kasen. Seasons recur. They may appear for up to five verses in a row. There are two spring blossom verses. There are three moon verses, two of which are generally autumn. Love appears as a fixed topic twice, potentially for an extended run. These factors make nonsense of the assertion that the principal motor of renku is absolute diversity. The structure of the Kasen clearly demonstrates that fine writing has more to do with periodicity and interlocking cycles, with tonal control and evolution.

And there's the rub. New or occasional writers of renku who have not yet refined their skills in these matters may find the Kasen simply too long. Without clear vision and leadership the twelve verses of a development side can rapidly become amorphous. The Kasen too takes time to complete. In the case of remote composition, by surface or email, the number of exchanges necessary to arrive at a full text may be so great as to cause the poem, or enthusiasm for it, to founder.

But the Kasen was and is essential to the development of all aspects of excellence in renku. A person who limits themselves always to the shorter contemporary forms is unlikely to develop the highest level of artistry that the genre permits.

Why would anybody want to listen to half a symphony, or view half a sculpture? Whilst it may be completed relatively rapidly The Han Kasen is so ugly and unbalanced that it barely serves as a practice piece. Its manifest deficiencies have been a principal factor in the search for more satisfactory short forms over the course of the last several decades.

The Triparshva is an excellent vehicle for exploring and expressing the techniques and sensibilities typical of the Basho school. Both preface and finale are the same length as those of the Kasen. The fixed topics of moon and blossom appear in familiar contexts, encouraging a classical approach.

At ten verses the single development movement is long enough to achieve extended tonal and dynamic effects. Love has sufficient space to develop without the risk of becoming dominant, and there is room for discretion as to where it appears.

With its twenty two verse six-ten-six structure the Triparshva has sufficient extent to sensibly permit ideas of renku as mandala - a poem that contains all things - whilst still being compact enough to facilitate remote composition, via email for instance. In short, the Triparshva is very hard to fault. Persons who do not have the time, space, confidence or inclination to compose a Kasen should seriously consider the Triparshva.

The folio structure of the Nijuin reflects that of the Kasen. It therefore divides its twenty verses between four faces or sides, each identified with an element of the jo-ha-kyu dynamic pattern. These sides are considered as preface, development part one, development part two, and rapid close, occupying four-six-six-four verses respectively. Each season features once, except for sequences begun in spring, in which case spring both starts and ends the poem. Spring and autumn verses tend to appear in clusters of three, winter and summer have one pair each. Seasons do not straddle the movement boundaries.

The Nijuin has two moon verses, one of which is always autumn. Except for sequences begun in spring the final face closely resembles the final face of the Kasen, spring blossom therefore appears in the penultimate position. For sequences begun in spring the topic of blossom often features in either hokku or wakiku, in which case it is absent from the finale. Blossom is generally treated as the traditional cherry or plum. The special compositional characteristics of hokku, wakiku, daisan and ageku are always respected.

Love may appear twice as a pair of verses midway on each of the two sides of development/intensification (ha). Alternatively love may appear once only as a cluster of three verses midway on either of the sides, in which case the first and last will tend to be written as usher-of-love (koi no yobidashi) and end-of-love (koi banare).

A feature of the renku renaissance underway since the latter half of the last century has been the search for new types of renku sequence that are shorter than the Kasen yet reflective of its general aesthetic characteristics. The popularity of the Nijuin is proof that its originator, Meiga Higashi, was successful in this quest. The Nijuin is clear, unambiguous, and effective.

There are some drawbacks. The preface can feel a little truncated as it is crowded with verses each having special compositional characteristics: hokku, wakiku, daisan and close. The division of the twelve verses of ha into two six verse sections may well mirror the symmetry of the Kasen but it does tend to limit the scope for extended tonal and dynamic effects. However these criticisms are marginal. Experienced writers will find ways to overcome them, whilst new and occasional writers of renku will benefit from the Nijuin's ease of assimilation.

The word Shisan has several layers of meaning. At a primary level it may be read as 'shi', meaning 'four', and 'san' meaning 'three'. When written in Chinese characters 'shi' (or 'tamawari') may be taken as 'a gift from a higher place', and 'san' (or 'bansankai') indicates a 'banquet' or 'formal meal'. For all its compaction therefore the Shisan is nonetheless an invitation to observe the finer points of style. Accordingly the Shisan respects the tonal and topical imperatives of the jo-ha-kyu dynamic pattern and honours the special compositional characteristics of hokku, wakiku, daisan and ageku.

What happens if you try to compress the vast scope of the Kasen into such a short space? You fail. In fairness this is not really what the Shisan attempts. But it does propose four movements phrased according to the principles of jo-ha-kyu and in this there are conflicts.

It is extremely difficult to establish the calm tone of the preface (jo) when all three constituent verses - hokku, wakiku and daisan - have special compositional requirements of their own. This is nowhere more apparent than for the third verse (daisan) which must at once 'break-away' from the more tightly paired hokku and wakiku, whilst conveying a sense of pause to mark the end of the preface.

By dividing into threes the Shisan also obliges both the first part of the development movement (ha part one) and the finale (kyu) to open with a short verse (tanku) - a marked contrast to the normal practice of beginning each movement with the apparently more authoritative long verse (chouku).

At first sight the adoption of the natural calendar may appear to be a welcome simplification. In practice it becomes considerably more difficult to establish a tangible non-season gap between seasonal clusters as there is a tendency for the mind to impute chronological references to the interstitial verses even where none are intended. For some the fact that spring blossom can no longer be relied upon to provide a graceful exit is also a drawback.

But the difficulties should not be overstated. The Shisan can be the vehicle for taught and finely structured writing as long as the temptation towards baroque intricacy is overcome.

The Junicho or Twelve Tone is a ‘single sheet’ poem that disregards all formal separations. Typically spring and autumn are each represented by a grouped pair of verses, winter and summer by one apiece as, for sequences begun in winter or summer, the convention that verse two (wakiku) should take the same season as verse one (hokku) is frequently disregarded.

The Junicho allows for a single bloom verse; this may appear in any season and be blossom or a generic flower. The poem likewise contains a single moon verse that may also appear in any season. Love will be represented by a grouped pair of verses that may appear in any position, but are unlikely to constitute the very beginning or very ending of a poem.

The particular compositional characteristics of hokku and ageku tend to be respected whilst those of wakiku and daisan may well be discarded. The topical and tonal exclusions common to the opening movements of more traditional types of sequence are ignored.

The Junicho is the most flexible of all formal types of contemporary mainstream renku and pays least regard to precedent. The name 'Twelve Tone' recalls Hauer and Schönberg and is taken by many as an invitation to consider each verse as a distinct pitch or colour.

It would be unfortunate though if the inference is drawn that the Junicho is composed of 12 separate verses, each of which seeks to be as distinct as possible. The musical analogy reminds us that there must be elements of coherence to balance those of divergence; the pursuit of diversity at all cost is likely to result in a poem that is harsh and uninflected.

Though they may be shorn of much classical precedent the fixed topics of moon, flower and love are none-the-less present, as are the conventional seasons. One could argue therefore that far from being the most open form of renku - and therefore ideally suited to persons new to the genre - the Junicho is in fact highly challenging and best approached with an awareness of precisely those sensibilities which it has, at first sight, eschewed.