# [r-t] Doubles 240s

Alexander Holroyd holroyd at math.ubc.ca
Thu Mar 26 10:41:41 UTC 2015

```OK, I have a suggestion.  Those who are concerned about this deep and
troublesome issue can use the following two terms from now on:

1. "Identity change in a type of performance in which rows are
traditionally repeated a number of times that is not necessarily specified

2. "Identity change in a type of performance in which the entire sequence
of rows (including any repeated rows) is typically specified in advance
(notwithstanding the possibility that a conductor may choose to vary the
calling on the fly)"

That way such people can be certain that repeated rows will never again be
the cause of them getting confused between the two settings.

In cases where it is clear from context which type of performance in being
discussed (which would be almost always, I suspect), users of the terms
should be free to abbreviate either to the shorter form "Identity change".

On Fri, 20 Mar 2015, Mark Davies wrote:

> 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
>
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```