Cameron Horsburgh wrote Monday, March 23, 2009 12:54 AM
I've had a problem with some auto beaming, and after some
discussion
on -user[1] I believe it's a limitation with LilyPond's
autobeaming
mechanism. Here's my problem:
I am setting a piece in 4/4 that has many examples of the figure
a8 a a a16 a
beginning on either the first or third beats of the bar. The
beaming
LilyPond gives me is
a8[ a a a16 a]
when I would prefer
a[8 a] a[ a16 a]
I had a go at writing a rule to get this behaviour but there
doesn't
sem to be any way of doing it. This was confirmed by Trevor
Daniels in
the discussion on -user.
This raises two questions: first, what should the default beaming
be
in this case? I don't see a lot of the one that LilyPond
generates,
and I find it reasonably hard to sight-read. Most scores I see
seem to
use the one I am trying to get.
Second, the autobeaming mechanism should allow this sort of
construct. The problem is that the beaming between the second and
third notes depends on the length of the fourth and fifth notes.
Or,
to quote Trevor,
You need some sort of back-tracking so that when the 16th notes
were
found the beaming was restarted using a different set of rules.
I imagine the first issue (if it is an issue) would depend on the
second issue being fixed, and I presume that would be a rather
difficult problem to solve. Still, if they are legitimate problems
I
think they rate a mention in the bug tracker.
Just to clarify, the problem is to automatically beam
the pattern with 16th as a[8 a] a[ a16 a] while _also_
beaming four 8ths as a8[ a a a]. That is, to end the
8th beam after two notes if later on it runs into 16th
but to continue otherwise. The first pattern on its own
can be done easily now.
Trevor
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