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;;; default setting: it changes in every generation the highest and lowest pitch by an OCTAVE 
;;; by changing :position (see examples) you could change which position should be changed/transposed
;;; default interval is 12


(defun chord-contraction/expansion (n pitchlist &key (position nil) (interval 12) (chord nil))
  (let* ((pitchlist (if (chordp (car pitchlist))
                      (melodize pitchlist)
         (position (if (null position)
                     (list 0 (1- (length pitchlist)))
                     (if (listp position)
                       (list position (- (1- (length pitchlist)) position)))))
         (pitchlist  (cons 
                      (loop repeat n
                        collect (setf pitchlist (sort-asc
                                                  (position-replace position 
                                                                     (pitch-transpose interval (list (nth (car position) pitchlist)))
                                                                     (pitch-transpose (neg! interval) (list (nth (cadr position) pitchlist))))
    (if (null chord)
      (chordize pitchlist))))

;;; EXAMPLES: evaluate by cmd3

(setf 12-tone-field '(f3 fs3 gs3 c4 d4 e4 b4 cs5 eb5 g5 a5 bb5))

(chord-contraction/expansion 4 12-tone-field :chord t)
=> ((f3fs3gs3c4d4e4b4cs5eb5g5a5bb5) (fs3gs3c4d4e4f4bb4b4cs5eb5g5a5) (gs3c4d4e4f4fs4a4bb4b4cs5eb5g5) (c4d4e4f4fs4g4gs4a4bb4b4cs5eb5) (d4eb4e4f4fs4g4gs4a4bb4b4c5cs5))

(chord-contraction/expansion 4 12-tone-field :chord t :interval 48)
=> ((f3fs3gs3c4d4e4b4cs5eb5g5a5bb5) (bb1fs3gs3c4d4e4b4cs5eb5g5a5f7) (f3fs3gs3c4d4e4b4cs5eb5g5a5bb5) (bb1fs3gs3c4d4e4b4cs5eb5g5a5f7) (f3fs3gs3c4d4e4b4cs5eb5g5a5bb5))

;;; with spezific positions (inner change)
(chord-contraction/expansion 4 12-tone-field :chord t :position 3)
=> ((f3fs3gs3c4d4e4b4cs5eb5g5a5bb5) (f3fs3gs3d4eb4e4b4c5cs5g5a5bb5) (f3fs3gs3cs4eb4e4b4c5d5g5a5bb5) (f3fs3gs3d4eb4e4b4c5cs5g5a5bb5) (f3fs3gs3cs4eb4e4b4c5d5g5a5bb5))

(chord-contraction/expansion 4 12-tone-field :chord t :position '(0 5))
=> ((f3fs3gs3c4d4e4b4cs5eb5g5a5bb5) (e3fs3gs3c4d4f4b4cs5eb5g5a5bb5) (f3fs3gs3c4d4e4b4cs5eb5g5a5bb5) (e3fs3gs3c4d4f4b4cs5eb5g5a5bb5) (f3fs3gs3c4d4e4b4cs5eb5g5a5bb5))

;;;; with different intervals

(chord-contraction/expansion 4 12-tone-field :chord t :interval 11)
=> ((f3fs3gs3c4d4e4b4cs5eb5g5a5bb5) (fs3gs3c4d4e4e4b4b4cs5eb5g5a5) (gs3c4d4e4e4f4bb4b4b4cs5eb5g5) (c4d4e4e4f4g4gs4bb4b4b4cs5eb5) (d4e4e4e4f4g4gs4bb4b4b4b4cs5))

(chord-contraction/expansion 4 12-tone-field :chord t :interval 7)
=> ((f3fs3gs3c4d4e4b4cs5eb5g5a5bb5) (fs3gs3c4c4d4e4b4cs5eb5eb5g5a5) (gs3c4c4cs4d4e4b4cs5d5eb5eb5g5) (c4c4cs4d4eb4e4b4c5cs5d5eb5eb5) (c4cs4d4eb4e4g4gs4b4c5cs5d5eb5))


Edited by AM
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hi julio


it's too complicated to share the code...the FUNCTION is made for a specific idea of the work (not common), so it's made for MY need...

here is a short sketch of the work... (part of it)


a) generating a pitch-sequence => by using a 12-tone-seq + its expansion by a sorting-algorithm (with GEN-SORT) => an INTERVAL-order mutates to a SCALE (see the list-plot)

b) pitches are projected on a sequence of symmetrical expanding/compressing FIELDS (with CHORD-CONTR...) => you see how the pitch-seq is contracted/exapnded in "space"


- result is a kind of interference of this processes => at the end you see (in list-plot) that the interference is going more and more to ONE LEVEL - to a SCALE 

- so its a kind of inside/out. the inherent structure, the inherent process/order is more and more recognizable during the process (start with compr/exp. 12-tone-row to the simple SCALE)






the project is a bit larger. this sequence (which rhythm is based on a binary-event-filter (data of a jpeg of an artist))  is only the structural background (some ideas developed by LACHENMANN) - on this NET (the score you see) there will be other GESTALTS/MOTIFS etc...

because my needs are such specific to my and my idea - most of the functions i had to code for myself, or modify/enlarge the OPMO functions, great that this is possible on this platform.


sorry a bit complicated and i can't not describe it properly with a few words 🧐





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I will share whatever I can as soon as I can.

I'm writing (notating) everything by hand ☠️  when composing and arranging.

I have used OM since day 1 and before that SCOM for many years.

Still I have  not learned much Lisp mainly caused by lack of time.

I use these tools mainly for chaotic experimenting I would say.


I have just quit working and is now a happy retired and hope to be able to spend more time wit OM and Lisp.



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