Lilypond functions

[Silvain Dupertuis]

Hello everyone,

Functions in Lilypond can also be written in pure Sheme syntax like this

#(define abcd
    (lambda (x y ... )

        PROCEDURE USING x y ...))

and then called within Lilypond with the syntax

\abcd x y ...

or within a Sheme fucntion with the syntax

(abcd x y ...)

If anyone is interested, I made an exercise for myself to explore the use of functions

and create a score of the first Prelude of Book I of J.S. Bach's Well-Tempered Clavier

As this piece has 32 bars using the same pattern based on 5 notes, plus an ending in 3 bars,

I used a simple list of notes (without any rythmic indications) as my main data
and designed functions to extract the groups of 5 notes, apply the patterns to create voices and scores, including a chord version on the piece in addition to the standard score.

notes = {
  c e g c e
  c d a' d f
  b d g d' f ... etc.

)

    Files (Lilypond, PDF and midi) are in this
      online folder
      (midi files need to be downloaded to listen to them)

Silvain Dupertuis

Merci

This is a perfect solution, and, a clear explanation about why my solution failed.  

Thank you very much

Ken Ledeen

Mobile:                617-817-3183

www.nevo.com 

www.bitsbook.com

tiny.cc/KenLedeen

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ᐧ

On Sat, Feb 27, 2021 at 10:43 AM Jean Abou Samra <jean@abou-samra.fr> wrote:

Le 27/02/2021 à 02:16, Ken Ledeen a écrit :

> I am struggling to understand the restrictions on substitution functions.
>
> For example:
>
> 1) can a function include "\score { ...}"  or can it only be invoked
> INSIDE a \score?
>
> 2) is it possible to include \header { ...}  inside a substitution
> function?  It fails when I try, but I don't understand why.
>
> I assume I am missing some basic concepts regarding their use.
>
> Thanks!


Hello,

Music functions must return music objects; \score blocks are not music
but general containers that enclose music as well as other objects such
as \header and \layout blocks.

However, replacing define-music-function with define-scheme-function,
you can define more versatile functions that are allowed to return any
kind of object for interpretation. For example:

\version "2.23.1"

failingFunction =
#(define-music-function () ()
    #{
      \score {
        \header {
          piece = "Piece A"
        }
        { c' }
      }
    #})

% \failingFunction

succeedingFunction =
#(define-scheme-function () ()
    #{
      \score {
        \header {
          piece = "Piece B"
        }
        { c' }
      }
    #})

\succeedingFunction


Hope that helps,
Jean