Re: Positioning volta bracket

[Jim Long]

On Tue, May 21, 2013 at 01:26:53PM +0200, Gregory Heytings wrote:
> 
> By the way, the question was: how is it possible to adjust the position by 
> hand (independently of the default position)?

In addition to the extra-offset method, there is another way.  I
most often adjust the Y-extent of the volta bracket.  This
effectively "lies" to lilypond's typesetting engine that the
volta bracket is vertically shorter or taller than lilypond would
normally think.  This affects not only how far above the staff
the volta is placed (as you requested), it also affects how much
space lilypond will reserve above the volta and below the staff
preceding the staff with the volta (the system-system spacing
for that one line).

I have a short three-line file that I read into my text editor
when I need it:

% decreasing the first number  increases the space BELOW the volta bracket
% increasing the second number increases the space ABOVE the volta bracket
\once \override Score.VoltaBracket #'Y-extent = #'(-1.0 . 1.0)

I don't know offhand what the default is, but I usually start at
-1.0 . 1.0 and adjust from there.  That starting point is
sometimes too crowded, but I read the comments and twiddle the
values until I get the output I want.  Want more space below the
volta?  Decrease the first number.  For less space below the
volta, increase the first number.  With negatives, remember that
going from -1.0 to -1.3 is a "decrease", and going from -0.8 to
-0.5 is an increase.  You can also adjust the space above the
volta (between the volta and system above it, if any) if you
like.

The effect is that, in addition to controlling *where* the volta
bracket is placed vertically, you can control the amount of
vertical space reserved for the bracket.  OTOH, extra-offset will
place the bracket where you want it vertically, but (to my
knowledge) will never change the page layout in terms of
system-to-system spacing, so it won't mess with your line/page
breaks.  That's good sometimes, but not others.

For instance, suppose you're setting a one-page piece, and it
just barely overflows to the second page, by only one
system/staff.  You tighten the fontsize and system-system spacing as
much as your aesthetics will allow, but it still overflows by just
one staff.  You notice that there is a little bit of extra
space under the volta bracket, so you use extra-offset to move
the volta bracket down.  That will move the bracket, but it won't
change the page layout, it will still overflow.

If you change the Y-extent so that lilypond thinks the volta
bracket is not as tall as it really is, lilypond will also adjust
the system spacing in the gap between systems where the volta
appears.  In some cases, scrunching the volta downward just slightly
may not only look a little bit better, but also give you that
slight bit of vertical reduction you need to get a page break
to land where you want it.  Another example is if the staff above
the volta has low notes that get too close, and you want the
volta to have more room above it.  Increase the second number in
the Y-extent and you'll get more space above the volta bracket.

Experiment a little until you get the hang of how to control
the vertical spacing above and below the volta bracket.

In this example, the first ending bracket has lots of space above
it, but not much below it.  The second ending has lots of space
below it, but not much above it.  Obviously in a real score, you'd be
making much subtler adjustments than these values, but it's just
an example to experiment with.

You *do* have to have the volta brackets on separate lines of your
layout (i.e. a \break between them) if you want to control their
Y-extent separately.  Otherwise, lilypond will keep them aligned
with each other.  Comment out the "\break" in the first ending to
see what I mean.

HTH,

Jim

%\version "2.16.2"

\score {
  \repeat volta 2 {
    \repeat unfold 16 g''4 \break
    \repeat unfold 16 g''4 \break
    \repeat unfold 16 g''4 \break
    \repeat unfold  8 g''4
  } \alternative {
   { % first ending
% decreasing the first number  increases the space BELOW the volta bracket
% increasing the second number increases the space ABOVE the volta bracket
    \once \override Score.VoltaBracket #'Y-extent = #'(-2.0 . 15.0)
    \repeat unfold  8 e''4
    \break
   }
   { % second ending
    \once \override Score.VoltaBracket #'Y-extent = #'(-15.0 . 2.0)
    \repeat unfold  8 c''4
   }
  } % alternative
} % score