It was when going into the chorus and I hit an Em instead of the Dm one touch. I'm not at the SXC900 right now but I entered the edit mode and step edit from the song menu. I hit play and the steps scrolled as it play and when it came to that chord I hit pause (not the square stop button) scrolled back a couple of lines and there it was, it was about 24 measures in, highlighted the note by touching and then I think I scrolled the wheel and got the Dm. This wasn't a serious recording just a "trial" and in the bridge I got distracted where I was and actually recorded an extra line. I played back and noted the measures, went to the editor and using multi button highlighted all those lines and deleted. Then saved and played back with correct chord. Came out seamless with the extra line gone.
One of those once you see how it's done it's pretty easy to do.