Re: Controlling stem lengths in a global way

[Aaron Hill]

On 2022-08-15 4:15 pm, Knute Snortum wrote:
> On Mon, Aug 15, 2022 at 4:00 PM Aaron Hill <lilypond@hillvisions.com> 
> wrote:
> > On 2022-08-15 3:11 pm, Knute Snortum wrote:
> > > I am engraving a piece where there are many groups of 16th notes where
> > > the first note is normal size and the rest should look like grace
> > > notes.  I'm using \scaledDurations, \magnifyMusic and \normalsize to
> > > do this, but I'm running into a systemic problem: the stems of the
> > > normal size notes are mostly too short (they'd be fine if they were
> > > grace notes).  To get around this I'm using beam position overrides
> > > and tweaks, but this gets tedious quickly.  Is there a) a systemic way
> > > to tweak the stem lengths, and/or b) better way for me to do this?
> > >
> > > %%%
> > > \version "2.22.2"
> > > \language "english"
> > >
> > > ns = \once \normalsize
> > >
> > > % Short stems on the normalsize notes
> > > \relative d'' {
> > >   \magnifyMusic #2/3 {
> > >     \scaleDurations 2/3 {
> > >       \ns d16 f, g c, f g  \ns c e, g c, e g
> > >       \ns c d, g c, d g  \ns c e, g c, e g |
> > >     }
> > >   }
> > > }
> > >
> > > beamPositionA = \tweak Beam.positions #'(4 . 2) \etc
> > > beamPositionB = \override Beam.positions = #'(3 . 1)
> > >
> > > % Need to tweak or override many, many notes
> > > \relative d'' {
> > >   \magnifyMusic #2/3 {
> > >     \scaleDurations 2/3 {
> > >       \ns \beamPositionA d16 f, g c, f g  \ns \beamPositionB c e, g c,
> > > e g
> > >       \ns c d, g c, d g  \ns c e, g c, e g \revert Beam.positions |
> > >     }
> > >   }
> > > }
> > > %%%
> > >
> > > --
> > > Knute Snortum
> >
> > Would \offsetting positions make more sense?  For instance, you could 
> > do
> > this:
> >
> > %%%%
> > ns = \once {
> >    \normalsize
> >    % Stem needs a little bit more length
> >    % to counteract magnifyMusic...
> >    \offset positions #'(1 . 0) Beam
> > }
> >
> > \relative d'' {
> >    \magnifyMusic #2/3 {
> >      \scaleDurations 2/3 {
> >        \ns d16 f, g c, f g
> >        \ns c e, g c, e g
> >        \ns c d, g c, d g
> >        \ns c e, g c, e g |
> >      }
> >    }
> > }
> > %%%%
> >
> > This does assume that the amount of lengthening required is uniform.
> >
> >
> > -- Aaron Hill
>
> Works like a charm.  Now I can have a couple of variables instead of
> dozens.  Thanks!

Another option is to use grob-transformer, which allows for smarter 
logic such as handling stem direction:

%%%%
ns = \once {
  \normalsize
  \override Beam.positions =
  #(grob-transformer 'positions (lambda (grob orig)
    (let ((dir (ly:grob-property grob 'direction)))
     (cons (+ (car orig) (* dir 0.75)) (cdr orig)))))
}

\relative d'' {
  \magnifyMusic #2/3 {
    \scaleDurations 2/3 {
      %% Some upward stem examples...
      \ns d16 f, g c, f g
      \ns c e, g c, e g
      %% Some downward stem examples...
      \ns f d' c e d c
      \ns g d' b f' d b |
    }
  }
}
%%%%


-- Aaron Hill