The 'open hierarchies' of the infinity series 

By Jørgen Mortensen The most amazing thing about Per Nørgård's infinity series is that one keeps on discovering the original row 'on another scale', that is, extended in time, at another pitch, inverted and noninverted. The individual musical element  the individual note  is not just simply a particular number in a particular series; it appears in an endless number of different contexts. Per Nørgård uses the term 'open hierarchy' to signify these characteristics, referring to the concept used by Arthur Koestler in Beyond Reductionism (London 1969). However, this notion of 'hierarchy' is somewhat different from the normal use of the term to indicate a pyramid of power. Koestler saw hierarchical organisation as a condition for life, and was one of those who paved the way for an holistic view of the world. In an open hierarchy the various layers are structurally connected, but no layer is superior to another. There is no final 'top' and no final 'bottom'. That this is also the case in Per Nørgård's infinity series can best be seen by the fact that one can rediscover the series by reducing the number of notes  by removing every 4th or 16th note  or by 'adding more notes on'. There are two concepts from fractal geometry which are well suited to illustrate the open hierarchy: selfsimilarity and scale invariance. The first concept indicates that the structure is found within the structure; the second one indicates that the structure reappears on another scale. Even the fact that now and then fragments of the original series appear within the series can be seen as an instance of selfsimilarity. 

The series contains the series, contains... 

No top,


Two mirror halves 
As the series is constructed by projection, it will be obvious that the two
halves mirror each other. Therefore, if we remove notes 0, 2, 4, 6... we get the series
inverted. If we remove notes 1, 3, 5, 7... we get the series noninverted again, only
transposed one step above the original  yet another instance of selfsimilarity. If we remove every fourth note (0, 3, 7, 11 ... ), we get the series in its original form, and this will also be the case if we remove every 16th note, every 64th note, etc. See the sample score below:


This score sample also reveals that every
time a new note appears it will form the basis of a new version of the series  transposed
and at another layer in terms of tempo. We have already seen this in the case of the
second note. The third note has the value 1 (F sharp). If we count from 0, we get the
following values: pn[2] =  1

