Re: wrong beamlet direction in 6/8 and 3/4 measure for dotted quaver and semiquavers

[Carl Sorensen]

On 1/16/12 3:41 PM, "Janek Warchoł" <address@hidden> wrote:

>Carl,
>
>Thanks for your research.
>I agree that there must be tied notes if one wants this melody to be
>in 3/4 meter.
>However, i'm not sure about 6/8.  My "pure reasoning" is that a
>measure in 6/8 meter divides like this:
>
>4. + 4.
>8+8+8  +  8+8+8
>(16+16)+(16+16)+(16+16)    +    (16+16)+(16+16)+(16+16)

This argument is hinted at on page 87 of Read.  It is also expressed
explicitly in Gould, page 157, where it indicates that reversing the
fractional beam indicates 6/16 (or 12/16) instead of 6/8, just as you
indicate below.

>
>If one wants to have
>16+16+16  +  16+16+16  +  16+16+16  +  16+16+16
>grouping, shouldn't 12/16 meter be used?

However, in the literature, there is talk of a "beat".  So Gould (p. 155)
says "Beams join notes within a beat, never across a beat".  In simple
time a beat is the denominator of the time signature.  In compound time, a
beat is three times the denominator of the time signature.  So a beat in
6/8 is *not* 1/8, but rather 3/8, as shown on p. 155 of Gould.

And there are cases in compound meters where we want to beat 3 against 2,
in which case the beaming that Martin asked for would be correct.

So maybe there should be a setting that allows one to choose which beaming
to use.

The rule that used to apply in 2.14 did not take into account beats at all
if there were fractional beams -- it just tried to avoid "sticking-out"
beamlets.  Sometimes it got it right, and sometimes it got it wrong.

Looking at Gould now, I think that you are correct, and 2.15.24 had it
right.

Maybe we should ask on -user?

Thanks,

Carl

P.S.  We can set context properties to get the desired behavior with
manual beaming:

\version "2.15.24"
\score {
  \relative c'{
    \time 6/8
    c16 d e f8.  c8. d16 e f
    \set Timing.baseMoment = #(ly:make-moment 1 16)
    \set Timing.beatStructure = #'(3 3 3 3)
    c16[ d e f8.]  c8.[ d16 e f]
  }
}