Extending LilyPond: 2.3.1 Context evaluation

### 2.3.1 Context evaluation

Contexts can be modified during interpretation with Scheme code. The syntax for this is

>     \applyContext function

`function` should be a Scheme function that takes a single argument: the context in which the `\applyContext` command is being called. The following code will print the current bar number on the standard output during the compile:

>     \applyContext
>       #(lambda (x)
>         (format #t "\nWe were called in barnumber ~a.\n"
>          (ly:context-property x 'currentBarNumber)))

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#### LilyPond — Extending