4. Understanding LilyPond grobs

LilyPond models music notation as a collection of graphic objects or grobs.

4.1. Grobs control typography

LilyPond grobs control the typographic details of the score:

\new Staff {
    c'4 (
    d'4 )
    e'4 (
    f'4 )
    g'4 (
    a'4 )
    g'2
}

In the example above LilyPond creates a grob for every printed glyph. This includes the clef and time signature as well as the note heads, stems and slurs. If the example included beams, articulations or an explicit key signature then LilyPond would create grobs for those as well.

4.2. Grobs can be overridden

You can change the appearance of LilyPond grobs with grob overrides:

\new Staff \with {
    \override NoteHead #'color = #red
    \override StaffSymbol #'color = #blue
    \override Stem #'color = #red
} {
    c'4 (
    d'4 )
    e'4 (
    f'4 )
    g'4 (
    a'4 )
    g'2
}

4.3. Check the LilyPond docs

New grobs are added to LilyPond from time to time.

For a complete list of LilyPond grobs see the LilyPond documentation.