Re: Beaming override problem

[Colin Hall]

On Mon, Jun 25, 2012 at 07:15:53AM +0200, David Kastrup wrote:
> Colin Hall <address@hidden> writes:
> 
> > On Mon, Jun 25, 2012 at 12:38:34AM +0200, David Kastrup wrote:
> >> Nick Payne <address@hidden> writes:
> >> 
> >> > If I set beamExceptions to beam 32nd notes by fours in 4/4 time, this
> >> > has the side effect of changing the beaming of 8th notes:
> >> >
> >> > %=====================
> >> > \version "2.15.40"
> >> >
> >> > changeBeaming = \set beamExceptions =
> >> >     #'((end . (((1 . 32) . (4 4 4 4 4 4 4 4)))))
> >> >
> >> > \relative c'' {
> >> >     c8 c c c c c c c
> >> >     \repeat unfold 32 { c32 }
> >> > }
> >> > \relative c'' {
> >> >     \changeBeaming
> >> >     c8 c c c c c c c
> >> >     \repeat unfold 32 { c32 }
> >> > }
> >> > %=====================
> >
> > Thanks for the report, Nick.
> >
> > I just checked the docs, Nick, and I agree with you that:
> >
> > "Beaming-rules is a scheme alist (or list of pairs) that indicates the
> > beam type and the grouping to be applied to beams containing notes
> > with a shortest duration of that beam type."
> >
> > would lead me to expect that an exception that only mentions 32nds
> > would only apply to 32nds.
> 
> It does.  But if he _replaces_ the existing list, previously entered
> exceptions are cleared out.

Thanks, David, that makes it plain.

I've re-read the docs and here is my new understanding:

Common time has already established some exceptions to the beaming
rules, which is why Nick's first bar is beamed in groups of four 8th
notes in the first place.

When he establishes an exception for 32nd notes the beaming for 8th
notes reverts to the standard behaviour of terminating a beam at the
end of a beat.

I now see that your sample works because you have built upon the
common time beamExceptions rather than simply replacing them.

I think the source of my confusion (and perhaps Nick's also) is that
the norm, to which we are creating an exception, is unclear.

He and I assumed that the normal behaviour is "what Lilypond does if I
make no special statements about beaming" whereas what normal actually
means is "terminate a beam at the end of a beat."

The behaviour of Lilypond does agree with the documentation so there's
no bug here.

Cheers,
Colin.

-- 

Colin Hall