adding chords to staff

Hello,

I'm trying to write a plugin that, given a score consisting of a single staff (with a melody), will create a new staff and add chords to that staff.

I can add a new staff easily enough (using cursor.appendPart()), but I'm unable to add anything to that staff (if I add a chord, it gets added to the original staff). I've tried a number of things on both MuseScore 1.2 and 2.0, but with no luck. Any help would be most appreciated.

Thanks,
Jon