Is Per Nørgård's infinity series unique? 

By Jørgen Mortensen Nørgård himself has said that he discovered rather than invented the infinity series. There is a sense in which it must always have existed, but apparently no one else has ever unearthed it, and certainly no mathematician or composer. A database containing various number series is to be found on the Internet: Sloane’s online Encyclopedia of Integer Sequences. The mathematician, N. J. Sloane, a member of AT & T Labs Research, edits the database. Nørgård's infinity series is included, and according to Sloane no one else has discovered it. However, the special version of the infinity series containing only two values is to be found under the name of the ThueMorse sequence. It is accompanied by the following explanation (for those who can understand it!): 'Follow a(0),..,a(2^k  1) by its complement'. 

The special characteristics of the infinity series 
One may therefore ask the question
whether there exist other series of numbers with the same characteristics as Nørgård's
infinity series. Put briefly, once can say that the special characteristics of the series
can be reduced to two conditions (after the first elements have been determined as 0 and
+1):
These are sufficient conditions for the creation of the
series. From the first if follows that every fourth note produces the series noninverted,
every eighth, the series inverted, every sixteenth, the series noninverted, and so on.
From the second condition it follows that the next new note in the series will
also form the series, further transposed and on another 'wavelength'  in the last
analysis, then revealing the special characteristic that each
new note recreates the series. (In fact, this is yet another way of constructing the
series  the sixth!). It would appear that other series which also possess this quality are to be found, for example, in irrational integers, but mathematicians have not yet apparently become aware of them. So strangely unique are the qualities of the infinity series! 

Noninversion/

However, it is relatively easy to
construct a single series with roughly the same qualities: if we change
one of the initial conditions in such a way that every other note recreates the series
noninverted instead of inverted, the following series appears: 

This series is mentioned in the section
on Construction with binary numbers. That
Nørgård has never found it interesting in musical terms is very understandable, as it
seems monotonous and mechanical. The conclusion
is, then, that Nørgård's infinity series is actually quite unique.

