1.2.2 LilyPond variables

LilyPond variables are stored internally in the form of Scheme variables. Thus,

twelve = 12

is equivalent to

#(define twelve 12)

This means that LilyPond variables are available for use in Scheme expressions. For example, we could use

twentyFour = #(* 2 twelve)

which would result in the number 24 being stored in the LilyPond (and Scheme) variable twentyFour.

Scheme allows modifying complex expressions in-place and LilyPond makes use of this ‘in-place modification’ when using music functions. But when music expressions are stored in variables rather than entered directly the usual expectation, when passing them to music functions, would be that the original value is unmodified. So when referencing a music variable with leading backslash (such as \twentyFour), LilyPond creates a copy of that variable’s music value for use in the surrounding music expression rather than using the variable’s value directly.

Therefore, Scheme music expressions written with the # syntax should be used for material that is created ‘from scratch’ (or that is explicitly copied) rather than being used, instead, to directly reference material.

See also

Extending: LilyPond Scheme syntax.