Re: Transposing in modes??

[Han-Wen Nienhuys]

Johannes Schindelin wrote:
> Hi,
>
> I always wanted to learn how to transform music with scheme, so I 
> implemented half of it. If some of you experts could look at it and tell 
> me what could be done more elegantly (Scheme is not my native language), 
> and especially what needs to be done to make this easy to use, that would 
> be super!
>
> Ciao,
> Dscho
>
>
>
> ------------------------------------------------------------------------
>
> #(define (scale-semitones scale)
>         "Get a vector of semitones for a given scale"
>         (if (equal? scale "ionian") #(0 2 4 5 7 9 11)
>         (if (equal? scale "dorian") #(0 2 3 5 7 9 10)

try (cond .. )

> #(define (alter-mode-aux music transpose-vector)
>                 "Transpose according to transpose-vector"
>                 (if (ly:music? music)
>                  (let ((pitch (ly:music-property music 'pitch)))
>                   (if (ly:pitch? pitch)
>                    (let* ((off (modulo (ly:pitch-semitones pitch) 12))
>                           (trans (vector-ref transpose-vector off)))
>                     (if (eq? trans null)
>                         (begin (display "Warning: Mode mismatch")
>                                 (display-music pitch))
>                      (if (not (eq? trans 0))
>                       (begin (set! pitch (ly:pitch-transpose pitch trans))
>                        (ly:music-set-property! music 'pitch pitch))))))))
>                 music)


I usually do

  (let* ((a (blah))
         (b (if (is-a? a) (blub a)  #f)
         (c (if (is-b? b) (blab b) #f))
          ...
         )

--
 Han-Wen Nienhuys - address@hidden - http://www.xs4all.nl/~hanwen