Fomus

(let ((c1 (fomus
       :output :chunk
       :global (list (make-timesig :off 0 :time '(5 8)))
       :auto-cautionary-accs t
       :parts
       (list
        (make-part
         :partid 'hp                ; identical ids are matched
         :name "Harpsichord"
         :instr :harpsichord
         :events
         (loop
          for off from 0 to 8 by 1/2
          collect (make-note :off off
                 :dur (if (< off 8) 1/2 1)
                 :note (+ 48 (random 25))))))))
      (c2 (fomus
       :output :chunk
       :global (list (make-timesig :off 0 :time '(5 8)))
       :auto-cautionary-accs t
       :parts
       (list
        (make-part
         :partid 'hp
         :name "Harpsichord"
         :instr :harpsichord
         :events
         (loop
          for off from 10 to 16 by 1/2
          collect (make-note :off off
                 :dur (if (< off 16) 1/2 1)
                 :note (+ 48 (random 25)))))))))
  (fomus (list c1 c2)
     :output '(:lilypond :view t)))