Hi List...
I've been looking for a way to define custom chord voicing (I wanted to
record all the back of the Jamey Aebersold books), and I came across
this post on stack exchange
(https://music.stackexchange.com/questions/15155/define-custom-chord-voicings-in-lilypond)
that almost did what wanted... In a reply to the question, someone
suggested the following, saying there was no way to avoid including the
duration parameter:
makevoicing = #(define-scheme-function (parser location m) (ly:music?)
(define-music-function (parser location d) (ly:duration?)
(map-some-music
(lambda (m)
(and (ly:duration? (ly:music-property m 'duration))
(begin
(set! (ly:music-property m 'duration) d)
m)))
(ly:music-deep-copy m))))
voicing = \makevoicing < g a c e a > % dom7, with 7th in bass
\new Staff {
% play the whole chord for two quarters, then a half
\voicing4 \voicing4 \voicing2
}
I modified the above to produce this:
makeVoicing =
#(define-scheme-function (parser location inversion) (ly:music?)
(define-music-function (parser location noteEvent) (ly:music?)
(map-some-music
(lambda (m)
(and (ly:duration? (ly:music-property m 'duration))
(begin
(set! (ly:music-property m 'duration) (ly:music-property noteEvent
'duration))
m)))
(ly:music-transpose (ly:music-deep-copy inversion)
(ly:music-property noteEvent 'pitch)))))
minorSevenI = \makeVoicing <ef bf d' f'>
dominantSevenI = \makeVoicing <e bf d' g'>
majorSevenI = \makeGuitarVoicing <e a d' g'>
\new Staff {
\minorSevenI c'4.
\dominantSevenI f8
\majorSevenI bes2
}
to allow me to specify the pitch and duration of the voicing. I was the
closest I though I could get to adding my own custom chord entry without
actually hacking the lilypond source.
So, I have a couple of questions, as this is my first excursion into
Scheme for LilyPond, or indeed Scheme period. First, in the manual, for
both define-scheme-function and define-music-function, it seems to say
that you need to declare the types of the parameters. So how come
'parser' and 'location' are not specified? I couldn't find anything in
the documentation about the first two parameters being the parser and
the location? The second question is: why the double definition? Why
define a music function inside a Scheme function? My first attempts at
achieving this before I found the above (which were moderately
successful but much more complicated than the above) used only a music
function. Does the original author know something I don't about how this
all works (my default assumption) or is it unnecessary?
So is this idiomatic Scheme? All suggestions gratefully received. I was
also trying to modify it so that I get notes that are below the twelfth
fret of a guitar, regardless of the octave of the pitch given. I have
had some success, but it basically relies on calling ly:music-transpose
twice, which seems a bit inefficient, so I'll not post that yet. If I
work out an efficient way of doing, would people be prepared to critique
it for me if I posted it?
Best regards,
Dave
