bad code but nice results... :-)

 

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;; rnd-symm-expand => generates rnd-symm transpositions
;;;; in different sequences (intervals, OMN-form,rhythms...
;;;; :chance => 0.0 - 1.0 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(defun rnd-symm-expand (seq &key (possible-intervals '(12 -12)) (chance 1))
  (let ((row)
        (firstpart)
        (rev-secondpart)
        (out))
    (setq row (if (pitchp (first seq))
                (pitch-to-midi seq)
                (append seq)))
    (setq firstpart (loop repeat (if (evenp (length row))
                                   (/ (length row) 2)
                                   (/ (1- (length row)) 2))
                      for cnt = 0 then (incf cnt)
                      collect (nth cnt row)))
    (setq rev-secondpart (loop repeat (if (evenp (length row) )
                                        (/ (length row) 2)
                                        (/ (1- (length row)) 2))
                           
                           for cnt = (- (length row) 1) then (decf cnt)
                           collect (nth cnt row)))
    
    (loop 
      for i in firstpart
      for j in rev-secondpart
      with int = 0 
      do (if (prob? chance)
           (setq int (rnd-pick possible-intervals))
           (setq int 0))
      collect (+ i int) into bag1
      collect (+ j (* -1 int)) into bag2
      when (= (length bag2) (if (evenp (length row))
                              (/ (length row) 2)
                              (/ (1- (length row)) 2)))
      do (if (evenp (length row))
           (setq out (append bag1 (reverse bag2)))
           (setq out (append bag1 (list (nth (length firstpart) row)) (reverse bag2)))))
    (if (pitchp (first seq))
      (midi-to-pitch out)
      (append out))))
    
;;;examples

(rnd-symm-expand '(0 0 0 0 0 0 0 0 0 0) :possible-intervals '(4 12 7) :chance 0.5)
(rnd-symm-expand '(1/4 1/4 1/4 1/4 1/4) :possible-intervals '(-1/32 1/32) :chance 0.5)
(rnd-symm-expand '(c1 c2 c3 c4 c5 c6) :possible-intervals '(1 -1) :chance 0.5)

 

Very very nice indeed !!

 

SB.

Final name and functionality:

(gen-transform '(0 0 0 0 0 0 0 0 0 0) :interval '(4 12 7) :prob 0.5)
(gen-transform '(1/4 1/4 1/4 1/4 1/4) :interval '(-1/32 1/32) :prob 0.5)
(gen-transform '(c1 c2 c3 c4 c5 c6) :interval '(1 -1) :prob 0.7)
(gen-transform '((c1 c2 c3) (c4 c5 c6)) :interval '(1 -1) :prob 0.7)
(gen-transform '((c1 c2 c3) (c4 c5 c6)) :interval '((1 -1) (-13 11)) :prob '(0.7 0.8))