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Re: Limitation with beat grouping

 From: Hans Aberg Subject: Re: Limitation with beat grouping Date: Mon, 23 Mar 2009 14:56:48 +0100

```On 23 Mar 2009, at 11:50, Cameron Horsburgh wrote:

```
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.

```
```
I'm not sure that's relevant---the behaviour happens regardless of
whether it starts on beat one or beat three.

The problem is that there is no way to tell the beamer to look forward
an arbitrary number of notes when deciding whether to beam or not. In
this case, the presence of a beam between the second and third notess
in the group is entirely contingemt on the presence of a fourth *and
fifth* note. If that fifth note exists, there shouldn't be a beam.

This is what Trevor means: when the beamer realises there is a fifth
note in the group (i.e. it's not four straight quavers) it needs to
'backtrack' and remove the beam between notes two and three.

Or have I mnisunderstood you?
```
```
```
See my other post. The normal way to beam is to select a meter, including metric accents and subaccents, thus building a hierarchical structures of subpatterns, and then let the beaming follow that. Though traditionally, one may not adhere to that very strictly, and more than one patten may be used, but perhaps not the same engraver in the same piece and meter.
```
```
Now, 4/4 is an exception to that in the higher number of such patterns that can be used. If one then wants to automate what traditionally is merely an ad hoc choice, then the problem is to lay down rules for that so that a computer program can do it.
```
Hans

```