Hi Wim,   a possible solution:   (setf chords (mclist (mapcar (lambda(x) ;; mapcar will apply the inversion to each chord (chord-inversion 3 x)) (harmonic-progression ;; harmonic progression definition (integer-transpose -1 '(1 2 3 4 5 6 7)) ;;degree for the chords '(c4 major) ;; scale used :size 4 ;; chords size )))) (setf drop2 (chordize