Substitution function syntax

Making a function that substitutes a variable into LilyPond code is easy. The general form of these functions is

function =
#(define-music-function
     (arg1 arg2 …)
     (type1? type2? …)
   #{
     …music…
   #})

where

argN	The nth argument.
typeN?	A Scheme type predicate for which argN must return #t.
…music…	Normal LilyPond input, using ‘$’ (in places where only LilyPond constructs are allowed) or ‘#’ (to use it as a Scheme value or music function argument or music inside of music lists) to reference arguments (e.g., ‘#arg1’).

The list of type predicates is required. Some of the most common type predicates used in music functions are:

• boolean?
• cheap-list? (use instead of ‘list?’ for faster processing)
• ly:duration?
• ly:music?
• ly:pitch?
• markup?
• number?
• pair?
• string?
• symbol?

For a list of available type predicates, see Predefined type predicates. User-defined type predicates are also allowed.

See also

Notation Reference: Predefined type predicates.

Extending LilyPond: Music functions.

Installed Files: lily/music-scheme.cc, scm/c++.scm, scm/lily.scm.