Fomus

(fomus
 :output '(:lilypond :view t)
 :quartertones t
 :parts
 (list
  (make-part
   :name "Flute"
   :instr :flute
   :events
   (loop
    for off from 0 to 10 by 1/2
    collect (make-note :off off
               :dur (if (< off 10) 1/2 1)
               :note (+ 70 (/ (random 4) 2)))))))