The PO-20 has pre-defined notes available for each chord. Here are all the notes:
No Chord 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 0 1 2 1 d m a b c d e f g a b c d e f g a 2 e m a b c d e f g a b c d e f g a 3 e sus a b c d e f g a b c d e f g a 4 e a b c d e f g# a b c d e f g# a 5 f a b c d e f g a b c d e f g a 6 g a b c d e f g a b c d e f g a 7 c/g a b c d e f g a b c d e f g a 8 e/g# a b c d e f g# a b c d e f g# a 9 am a b c d e f g a b c d e f g a 10 c/a a b c d e f g a b c d e f g a 11 dm/a a b c d e f g a b c d e f g a 12 d/a a b c d e f# g a b c d e f# g a 13 a a b c# d e f# g a b c# d f# g a 14 b/a a b c# d# e f# g# a b c# d# f# g# a 15 c a b c d e f g a b c d e f g a 16 d a b c d e f# g a b c d e f# g a