Re: Revised autobeam settings patch -- cleaned up debug comments (issue1667044)

[Trevor Daniels]

Carl, you wrote Monday, June 21, 2010 10:10 PM

Sorry for the delay - I've been away and it took
a while to catch up with my mail.

> On 6/16/10 3:18 AM, "Trevor Daniels" <address@hidden> 
> wrote:
> > Carl.D.Sorensen wrote Tuesday, June 15, 2010 11:27 PM
> >
> > > Description:
> > > Revised autobeam settings patch -- cleaned up debug comments
> > > in code and eliminated the irrelevant changes in
> > > Documentation/snippets just due to running makelsr.py
> > >
> > > Please review this at http://codereview.appspot.com/1667044/show
> >
> > One or two of the default beam settings might be
> > improved (while you're changing the beaming, that is - I
> > think the behaviour below is probably as in the current
> > releases, not introduced in this patch).  The most
> > important is illustrated by
> >
> > \relative c' {
> >   \time 3/4
> >   % In 3/4 time never beam an odd number of 8th notes or two
> >   % 8th notes in different beats
> >   f8 f f f f f
> >   f16 f f f f f f f f f f f
> >   f32 f f f f f f f f f f f
> >   f f f f f f f f f f f f
> >   f4 r8 f f f     % incorrect!
> >   f8 f~f f f f    % incorrect!
> >   d'4. c8 b8. a16  % incorrect!
> > }
>
> I accepted your statement of beaming rules, since
> I'm quite a novice at beaming.

Well, I'm no expert either.  My snippet above is based
on Ross, p 92, which says "Do not notate a 3/4 measure
that looks like a measure in 6/8 time."  Poor English,
but he goes on to show the first two of the three
examples marked incorrect above, and clearly labels them
as incorrect.

> And I adjusted the the autobeaming code so it would work according
> to your recommendations.
>
> Today I've been studying books to see what the references say, 
> because the
> new rule I added caused a regression in 4/4 time.
>
> I want to get some clarification.  If I understand your rules 
> correctly, you
> believe that
>
> f4 r8 f8[ f f]
>
> would be incorrect beaming, and that instead it should be beamed
>
> f4 r8 f8 f8[ f]

Yes; Ross gives exactly these patterns later on p 92 and labels them
incorrect and correct respectively.  That's where my snippet came
from.

> Ross, however (1970, page 92) shows the first pattern as "Another 
> use of the
> beam in 3/4 time", rather than as an incorrect use.

Hhm.  Maybe we are looking a different editions.  All I can
see earlier on p 92 are examples that don't contain rests, and
it is the presence of the rest that is important, since this
causes three quavers to be beamed together, making it look like
a 6/8 measure.

> The algorithm I developed to resolve that problem led to the 
> following inT
>
> r8 f8 f8[ f] f8[ f f f]
>
> where we previously had
>
> r8 f8[ f f] f8[ f f f]
>
> Ross (1970, page 91) shows the following as an acceptable beaming 
> in 4/4
>
> r8 f8[ f f] f4 f8[ f]
>
> Which would imply the the previous beaming is correct.

Agreed, although I don't think the new beaming here is as bad
as making a 3/4 measure look like one in 6/8.

> The bottom line is that the new beaming rules solve the first and 
> third
> incorrect cases in your example above.  However, the price of 
> doing that is
> they split a previously acceptable beam in 4/4 time.
>
> Let me summarize:
>
> OLD                       NEW
> 3/4
> f4 r8 f8[ f f]            f4 r8 f8 f8[ f]
> f4. f8[ b8. a16]          f4. f8  b8.[ a16]
>
> 4/4
> r8 f8[ f f] f8[ f f f]   r8 f8 f8[ f] f8[ f f f]
>
> So are these beaming rules correct, or at least better than the 
> old ones?

I think they are better than the old ones, but I'd prefer
to hear opinions from some real musicians.

> > I think here it would be better to break quaver beams
> > every beat
>
> For measures consisting entirely of quavers, beaming in 6 is far 
> preferable,
> in my opinion (and we've had this discussion before; we decided 
> that staying
> in 6 was best).

Agreed; I suggested this only as a possible way of avoiding
making a 3/4 measure look like one in 6/8.  Now you've
found a better solution for that we should continue to
beam 6 quavers in 6.

> Carl

Trevor