LilyPond Beginnershandleiding

Hoofdstuk 4: Tweaking output 89
These, then, are the main terms relating to objects which we shall use in this chapter.
4.1.3 Naming conventions of objects and properties
We met some object naming conventions previously, in Sectie 3.3 [Contexts and engravers],
pagina 59. Here for reference is a list of the most common object and property types together
with the conventions for naming them and a couple of examples of some real names. We have
used ‘A’ to stand for any capitalized alphabetic character and ‘aaa’ to stand for any number of
lower-case alphabetic characters. Other characters are used verbatim.
Object/property type Naming convention Examples
Contexts Aaaa or AaaaAaaaAaaa Staff, GrandStaff
Layout Objects Aaaa or AaaaAaaaAaaa Slur, NoteHead
Engravers Aaaa aaa engraver Clef engraver,
Note heads engraver
Interfaces aaa-aaa-interface grob-interface, breakaligned-interface
Context Properties aaa or aaaAaaaAaaa alignAboveContext, skipBars
Layout Object Properties aaa or aaa-aaa-aaa direction, beam-thickness
As we shall see shortly, the properties of different types of object are modified by different
commands, so it is useful to be able to recognize the types of objects and properties from their
names.
4.1.4 Tweaking methods
The \override command
We have already met the commands \set and \with, used to change the properties of contexts
and to remove and add engravers, in Sectie 3.3.4 [Modifying context properties], pagina 63, and
Sectie 3.3.5 [Adding and removing engravers], pagina 67. We must now introduce some more
important commands.
The command to change the properties of layout objects is \override. Because this command
has to modify internal properties deep within LilyPond its syntax is not as simple as the
commands you have used so far. It needs to know precisely which property of which object in
which context has to be modified, and what its new value is to be. Let’s see how this is done.
The general syntax of this command is:
\override Context.LayoutObject.layout-property = #value
This will set the property with the name layout-property of the layout object with the name
LayoutObject, which is a member of the Context context, to the value value.
The Context may be omitted (and usually is) when the required context is unambiguously
implied and is one of lowest level contexts, i.e., Voice, ChordNames or Lyrics, and we shall omit
it in many of the following examples. We shall see later when it must be specified.
Later sections deal comprehensively with properties and their values, see Sectie 4.2.3 [Types
of properties], pagina 98. But in this section we shall use just a few simple properties and values
which are easily understood in order to illustrate the format and use of these commands.
LilyPond’s primary expressions are musical items like notes, durations, and markups. More
basic expressions like numbers, strings, and lists are processed in ‘Scheme mode’, which is invoked
by prefixing the value with ‘#’. Although the values may sometimes have a valid representation
in LilyPond’s musical mode, this manual will always use ‘#’ for their entry for the sake of
consistency. For more information about Scheme mode, see Sectie “LilyPond Scheme syntax” in
Uitbreidingen.