Re: Changing autobeaming for 4/4 time

[Trevor Daniels]

Carl, you wrote Monday, August 10, 2009 10:58 PM
> On 8/10/09 9:14 AM, "Trevor Daniels" <address@hidden> 
> wrote:
> > With all Carl's mods applied just the expected two 
> > inconsistencies
> > remain:
> >
> > \relative c'' {
> >   a8 a a16 a a8 a a a a16 a | % wrong, should be ...
> >   a8 a a16[ a a8] a a a[ a16 a] |
> >
> >   a32 a a16 a a a a32 a a16 a a a a32 a a16 a a a a32 a | % 
> > wrong,
> > should be ...
> >   a32[ a a16 a a] a[ a32 a a16 a] a[ a a32 a a16] a a a a32 a
> > }
> >
> > The second of these can be fixed (bypassed really) with
> >
> > \overrideBeamSettings #'Score #'(4 . 4) #'end #'(((1 . 32) . (8 8 
> > 8
> > 8)))
> >
> > which I think is a more acceptable beaming anyway,
> > but the first is a more fundamental problem which cannot be
> > fixed by any override which preserves beam breaks at
> > 1/4, 1/2 and 3/4 AFAICS.
>
> OK, so now I can see the differences.  Thanks, Trevor.
>
> Can you express in words a rule that describes why
>
> a8 a a16[ a a8] a a a[ a16 a16]
>
> is better than
>
> a8[ a a16 a a8] a8[ a a a16 a]
>
> ?  It seems to me that something has triggered a desire to break 
> the beam on
> the beats, when
>
> a8[ a a a] a[ a a a]
>
> is desired to break at 1/2.
>
> Perhaps if you can explain this, I can figure out what is missing 
> in the
> autobeaming algorithms.

I can do no better than quote Ross:

1. [in 4/4 time] "A beam can never be used
  to combine notes of the second and third
  beats into a unit."

2. "In simple time any beat divided into
  more than two parts cannot be connected
  to another beat to form a unit."

Apart from these there are no firm rules,
but these explain my beaming.  Rule 1 permits
beaming 4 quavers (sorry, 8th notes) together
(and this seems the common practice), as
quavers have only two parts to a beat, but as
soon as two 16th notes are introduced we have
(at least) three parts to a beat, and rule 2
kicks in, forcing beams to be limited to
single beats.

HTH

Trevor