mpdolce - LilyPond

Chapter 4: Tweaking output 86
This looks a good bet to change the heaviness. It tells us that the value of thickness is a
simple number, that the default value is 1.2, and that the units are in another property called
line-thickness.
As we said earlier, there are few to no explanations in the IR, but we already have enough
information to try changing the slur thickness. We see that the name of the layout object is
Slur, that the name of the property to change is thickness and that the new value should be
a number somewhat larger than 1.2 if we are to make slurs thicker.
We can now construct the \override command by simply substituting the values we have
found for the names, omitting the context. Let’s use a very large value for the thickness at first,
so we can be sure the command is working. We get:
\override Slur #'thickness = #5.0
Don’t forget the #' preceding the property name and a # preceding the new value!
The final question is, ‘Where should this command be placed?’ While you are unsure and
learning, the best answer is, ‘Within the music, before the first slur and close to it.’ Let’s do
that:
{
}
\time 6/8
{
% Increase thickness of all following slurs from 1.2 to 5.0
\override Slur #'thickness = #5.0
r4 b8 b[( g]) g |
g[( e]) e d[( f]) a |
a g
}
\addlyrics {
The man who feels love's sweet e -- mo -- tion
}
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The man who feels love's sweet e motion
and we see that the slur is indeed heavier.
So this is the basic way of constructing \override commands. There are a few more complications
that we shall meet in later sections, but you now know all the essentials required to
make up your own – but you will still need some practice. This is provided in the examples
which follow.
Finding the context
But first, what if we had needed to specify the Context? What should it be? We could guess
that slurs are in the Voice context, as they are clearly closely associated with individual lines of
music, but can we be sure? To find out, go back to the top of the IR page describing the Slur,
where it says ‘Slur objects are created by: Slur engraver’. So slurs will be created in whichever
context the Slur_engraver is in. Follow the link to the Slur_engraver page. At the very
bottom it tells us that Slur_engraver is part of five Voice contexts, including the standard
voice context, Voice, so our guess was correct. And because Voice is one of the lowest level
contexts which is implied unambiguously by the fact that we are entering notes, we can omit it
in this location.
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