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Re: Limitation with beat grouping


From: Hans Aberg
Subject: Re: Limitation with beat grouping
Date: Mon, 23 Mar 2009 14:49:37 +0100

On 23 Mar 2009, at 09:26, Trevor Daniels wrote:

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.

Now I see what the problem is. In fact, Hindemith, "Elementary Training" gives the following 4/4 patterns (x an eighth note):
  (1)  [x x] [x x] [x x] [x x]
  (2)  [x x x x] [x x x x]
  (3)  [x x] [x x] [x x x x]
  (4)  [x x x x] [x x] [x x]
So one has a choice of beaming, here. ...

The problem, as I see it, is tied to the metric interpretation of 4/4, which is ambiguous: it can be taken as a strong beat (metric accent) on 1 followed by weaker on 2, 3 and 4. Alternatively, 3 can be accented more than 2 and 4, but less that 1:
     |   |   |   |
 4a  >   -   -   -
 4b  >   -  (>)  -

Then 4a gets the beaming with the 1/4 note groups together and the second gets the beaming with the 1/2 note groups together.

If this is the accepted standard then there is no
problem with LilyPond as it stands.  Either of these
two patterns can be specified by overriding the
current beam-ending rules.  What can't be done is to
mix the two stress patterns depending on beam duration.

... But if beaming should correspond to metric accent patterns, as in other meters, then this implies a shift of those, that is formally, these are different meters.
      |   |   |   |
 (1)  >   -   -   -    1+1+1+1
 (2)  >       -        2+2
 (3)  >   -   -        1+1+2
 (4)  >       -   -    2+1+1

So as you say, instead of choosing meter (with accent pattern), and let the beaming follow that, one wants to do the other way around.

If this is not just a tradition of being sloppy with beaming, I wonder what the underlying rule might be.

  Hans






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