here is a little "sketched" function STEP-TO-PITCH , perhaps OM could further develop the function...   ;;; FUNCTION (defun step-to-pitch (&key steps pitches start) (let ((pos (car (position-item start pitches)))) (append (list (nth pos pitches)) (loop for i in steps ;; setting pos by add the step to pos do (setf pos (+ pos i)) ;; when pitch-range to small then reset to lowest pitch+step ;; could be a more in