Re: Help with Auto-beaming rules

[Simon Albrecht]

Hello Richard,

Am 08.09.2015 um 13:43 schrieb Richard Shann:
> The attached bit of 18th century typesetting shows an 8.[ 32 32] beamed
> group and a series of  32[ 32 32  32] beamed groups in a 2/4 time
> signature. This is quite typical of the period and is IMHO more legible
> than if the 1/32 notes were beamed in larger groups.

Of course.

> Can this be done by auto-beaming rules in LilyPond?
> My attempt follows - I have created two bars beamed manually and
> followed with two bars which I hope to auto-beam by feeding the first
> two bars to  \beamExceptions.
> 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8>< 8><
>
> \version "2.19.5"
> MvmntIVoiceI = {
>           e''8.[ fis''32 g''] e''8.[ fis''32 g'']
>           c'32[ d'32 e' f'] c'32[ d'32 e' f'] c'32[ d'32 e' f'] c'32[ d'32 e' 
> f']
>           c'32 d' e' f' c' d' e' f' c' d' e' f' c' d' e' f'
>           e''8.( fis''32 g'') e''8.( fis''32 g'')
>
> }
> \layout {
>      \overrideTimeSignatureSettings 2/4 1/4 #'(1 1) \beamExceptions { 8.[ 32 
> 32] 8.[ 32 32] |

OK, the problem is that the NR doesn’t describe the limitations set for 
using \beamExceptions. One exception can always only use one duration, 
not different ones. This is because internally \beamExceptions creates a 
Scheme nested list of the type used in scm/time-signature-settings.scm, 
where each ‘exception rule’ is of the form ((1/32 . (4 4 4 4))). And 
there’s no way of translating { 8.[ 32 32] 8.[ 32 32] } into such a rule.

> Be that as it may, I would like to be sure that this beaming cannot be
> done with a single \overrideTimeSignatureSettings at the outermost
> context, that is, that individual passages will need to be marked to
> achieve the desired beaming.

Yes, this will require manual beaming.

Yours, Simon