Jeff Dunn:

>Then there are the strange numbering systems of the avant garde. I hope
>experts out there can provide interesting examples. I've seen decimals
>used, although Roman numerals seem to be more common.

The Australian composer Carl Vine's fourth symphony, which is not avant
garde, is called Symphony No 4.2 to reflect the fact that it underwent
revision.  Would that Bruckner had followed a similar practice!

Richard Pennycuick