Re: Limitation with beat grouping

[Cameron Horsburgh]

On Mon, Mar 23, 2009 at 09:47:22AM +0100, Hans Aberg wrote:
> On 23 Mar 2009, at 01:54, Cameron Horsburgh wrote:
>
>> 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 am not sure what you mean here. Can you give an example?
>
> 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?


-- 

Cameron Horsburgh

Blog: http://spiritcry.wordpress.com/