# LilyPond context concatenation¶

Abjad users should know this: LilyPond lets you use a control file to glue together separate LilyPond files that segment your score into horizontal chunks of music. Abjad calls this feature “LilyPond context concatenation.”

Consider adding this pattern to your workflow. The motivation is performance. Shorter score semgents will always compile faster and be easier to debug than longer score segments.

Preliminaries. The following two LilyPond examples produce identical output.

Without context concatenation:

```\context Score = "Score" {
\context Staff = "Violin" { c'4 d' e' f' g' a' b' c'' }
}
```

With context concatenation:

```\context Score = "Score" {
\context Staff = "Violin" { c'4 d' e' f' }
\context Staff = "Violin" { g' a' b' c'' }
}
```

The reason this works is because the two staff contexts share the same name: `"Violin"`.

This shows that you can segment LilyPond input into horizontal chunks. Doing this in a single file, like here, isn’t highly motivated. But this is the simplest way to illustrate the feature.

The pattern. LilyPond’s context concatenation becomes highly motivated when we ask LilyPond to glue together entire scores written in separate files.

The simplest example requires three files:

• `music.ly`

• `segment-01.ily`

• `segment-02.ily`

Contents of `music.ly`:

```\version "2.21.80"
\language "english"

\score
{
{
\include "segment-01.ily"
\include "segment-02.ily"
}
}
```

Contents of `segment-01.ily`:

```\context Score = "Score"
{
\context Staff = "Violin" { c'4 d' e' f' }
}
```

Contents of `segment-02.ily`:

```\context Score = "Score"
{
\context Staff = "Violin" { g'4 a' b' c'' }
}
```

Calling LilyPond on `music.ly` produces a single score with a single staff.

The reason this works is because the two staff contexts share the same name AND because the two score contexts share the same name: `"Vioin"` and `"Score"`, respectively.

Discussion.

• LilyPond context concatenation becomes essential to Abjad users during score build.

• Score build best practices do not yet appear in Abjad’s docs. But, in short, building a score means creating a build directory, adding assets to it, and producing a PDF of your score for distribution. Part of this involves collecting LilyPond files produced separately for each score segment and gluing them together. LilyPond context concatenation makes that possible.

• LilyPond context concatenation is the reason real-world scores composed in Abjad use LilyPond’s `\context` command instead of LilyPond’s `\new` command. Only LilyPond contexts created with LilyPond’s context command can be named. Only named contexts can be concatenated.

• LilyPond filename suffixes are conventional.

• Abjad users conventionally add `.ly` to mark the control file in multifile patterns like this one.

• Abjad users conventionally add `.ily` mark included files.

• The recommended naming pattern Abjad score directories specifies two-digit Arabic numerals `01`, `02`, `03` beginning at one.

• The recommended naming pattern for LilyPond files extracted from segment directories specifies hyphen-delimited lowercase filenames `segment-01.ily`, `segment-02.ily`, `segment-03.ily` that correspond to the directories in which they were created.