Re: GOP2-3 - GLISS or not

[Joseph Rushton Wakeling]

On 30/07/12 17:52, Graham Percival wrote:
> In general, yes.  But some aspects of our syntax haven't been
> around for a long time -- footnotes, woodwind fingering, compound
> meters, etc.  Do we have the best syntax for those?  I mean,
> maybe David can figure out a way to allow us to write
>    \compoundMeter (3+2)/8
> or simply
>    \time (3+2)/8
> instead of
>    \compoundMeter #(3 2 8)

That's another very good case for careful thought.  Just some examples of what 
you might have to handle if you want to cover the gamut of expression in 20th 
century notation:

     (3+2+3)/8

     3/8 + 2/8 + 3/16

     (3+2)/8 + 3/16

     3.5/8   [or  (3+1/2)/8 ...]

     (2 + 1/3)/4   [Boulez in Le Marteau Sans Maitre]

     4/8 + 1/10

     3/8 + 4/10 + (3+2+2)/12

Note that these are all _logical_ extensions of traditional time signatures. 
There's no reason in principle why they can't all be supported.  But (just as an 
example) if you try,

  \compoundMeter #'((3 2 3 8) (1 10))

  c'4. c'4 c'4. \times 4/5 { c'8 } |
  c'4. c'4 c'4. \times 4/5 { c'8 } |

... with current Lilypond, you get an error:

  warning: strange time signature found: 11/10
  ERROR: In procedure ly:make-moment:
  ERROR: Wrong type argument in position 1 (expecting integer): 15/4

... even though Lilypond supports so-called "irrational meters" like 3/10, 
11/24, etc. (and if you replace the compound meter in the above example with a 
straightforward 11/10 time signature, it works fine).

You get a similar error with the following:

  \compoundMeter #'((4 2/3 4))

  c'4 c'4 c'4 c'4 \times 2/3 { 4 } |
  c'4 c'4 c'4 c'4 \times 2/3 { 4 } |

That is,

  Parsing...ERROR: In procedure ly:make-moment:
  ERROR: Wrong type argument in position 1 (expecting integer): 14/3

... which can again be avoided by using the equivalent time signature of 7/6.

This is probably actually quite easy to fix, but _as things stand_ it seems to 
me that compound time signatures probably need some careful consideration with 
respect to the styles and use-cases out there.

Based on the above it's _probably_ just an internals issue and not a syntax 
problem (I can make bug reports accordingly), but it's another contemporary 
music issue to throw into the mix regarding syntax.