To move the midi from the old instrames we dragged the two tracks under each other and then dragged and dropped the midi clip down to the new instrument. If we was using two different projects I would export all the midi in the old project out as midi files and imported it that way but since we decided to work in one project we chose the drag and drop method instead.
While we were moving the Midi to their new instruments we also changed the placement of some of the midi clips to make the feel be different and also to work with the different style that the new instruments was presenting.
There was one section where we took off a MIDI based guitar and moved to a wavetable synth and it didn't feel right at all so we rewrote it to make it feel more part of the track and not odd and out of place.