Fomus

(fomus
 :output '(:lilypond :view t)
 :parts
 (list
  (make-part
   :name "Piano"
   :instr :piano
   :events
   (loop repeat 10
     for off = (random 30.0)
     and dur = (1+ (random 3.0))
     collect (make-note :off off :dur dur :note (+ 60 (random 25)))))))