Generating symmetry-based forms

The following function generates symmetrical structures based on sequences of tones, which can evolve over multiple generations, resulting in nested symmetries. Here are a few examples mapped to pitches, integers, and rhythms.

(defun gen-symmetrical-structure (&key row gen)
  (let* ((seq1 (filter-repeat 1 (loop repeat gen
                                     for i in (rnd-sample '(3 5 7 11) :norep t)
                                     append (progn
                                              (setf r1 (filter-first 11 row))
                                              (setf r2 (filter-last 11 row))
                                              (setf n i)
                                              (setf rev (probp 0.5))
                                              (setf r1 (if (null rev)
                                                           r1
                                                         (reverse r1)))
                                              (setf r2 (if (null rev)
                                                           r2
                                                         (reverse r2)))

                                              (flatten (gen-rotate (random 2) (list (filter-first n r1)
                                                                                    (filter-last n r2))))))))

         
        (seq2 (flatten (gen-rotate (random 2) (list (filter-first (length seq1) seq1)
                                                    (pitch-invert-start 'fs4 (reverse (filter-first (length seq1) seq1))))))))
        (filter-repeat 1 (flatten seq2))))


;; with one GEN
(pitch-list-plot
 (gen-symmetrical-structure :row (rnd-air :type :pitch) :gen 1)
 :join-points t :style :fill)

;; with x GEN
(pitch-list-plot
 (gen-symmetrical-structure :row (rnd-air :type :pitch) :gen (+ 2 (random 10)))
 :join-points t :style :fill)


;; remapped to integer
(list-plot
 (pitch-to-integer (gen-symmetrical-structure :row (rnd-air :type :pitch) :gen (+ 2 (random 10))))
 :join-points t :style :fill)

=> (9 5 7 1 10 11 4 8 3 2 0 6 9 5 7 1 10 11 4 8 3 2 0 2 3 8 4 1 7 5 9 6 0 2 3 8 4 11 10 11 10 1 7 5 9 6 3 7 5 11 2 1 2 1 8 4 9 10 12 6 3 7 5 11 8 4 9 10 12 10 9 4 8 1 2 11 5 7 3 6 12 10 9 4 8 1 2 11 5 7 3)

;; remapped to lengths
(length-list-plot
 (gen-length (pitch-to-integer (gen-symmetrical-structure :row (rnd-air :type :pitch) :gen (+ 2 (random 10))))
             '1/32)
 :join-points t :style :fill)

=> (11/32 3/32 9/32 5/16 3/8 3/16 1/16 7/32 5/32 1/8 1/16 7/32 5/32 1/8 1/32 1/4 11/32 3/32 9/32 5/16 3/8 3/16 1/16 7/32 5/32 1/8 1/32 1/4 11/32 3/32 9/32 5/16 1/16 3/32 9/32 1/32 1/8 11/32 1/4 7/32 5/32 5/16 3/16 -1/32 1/16 3/32 9/32 1/32 1/8 11/32 1/4 7/32 5/32 5/16 1/4 7/32 5/32 5/16 3/16 -1/32 1/16 3/32 9/32 1/32)