All the chord sequencer does is remember the sequence of the chords! I believe that if you play it back you can hit the transpose button and it will modulate, along with everything else.
Good news is that with the BK9 you can SAVE the file, unlike on Korg's. I didn't go into this, but if it saves it as a midi file you could then edit and transpose. May be worth exploring. I think that what your friend needs to do is just record a simple midi file.