[r-t] Doubles 240s

[Mark Davies]

Ander writes,

> Why on earth is any of this relevant?  If the same row is rung twice, then
> the transformation from one to the other is the identity permutation.

But, as Martin Bright has pointed out, there is actually a difference 
between "ringing the same row twice", and the identity change as we have 
been discussing it.

In a performance of 60 on Thirds, there appear to be identity changes 
between the called changes (which are all non-identity). However the 
exact number of these is not material to the performance. Conversely, in 
a multi-extent block of Minor with a row such as 123456 repeated in the 
middle, the identity change is a material part of the performance - 
there must be one and only one, if the length and truth of the 
performance is to be correct.

You could argue that this is simply the difference between the two types 
of performance, however it does show there is a clear difference in 
treatment between two things which, if tagged with the word "identity 
change", appear to be the same. And even in the Minor peal, the rounds 
rows before and after are more similar to the identity changes in the 
call-change peal than they are to the repeated 123456 in the middle of 
the MEB.

To muddy things further, what if the MEB started with seven rows of 
rounds? How would we distinguish the six "material" identity changes 
required for this start from the indeterminate number of non-material 
identity changes in the rounds beforehand?

I just don't like this very much!

MBD