I'm just browsing this thread on a mobile on a camper holiday (so no PC or Genos with me as a reminder) but the way I do it, from memory, once you have:
1. set up numbered Registrations for songs,
2. made a basic cut-down midi template on the Genos to 'talk to' the iPad/OnSong
3. setup on MIDI B not A,
3. understood the Genos MIDI Multi Recording function, to set up a small song file containing the song's Program Change number,
4. Saved this midi 'song' to the song Registration
5. Not forgetting to then save the Registration itself,
then you only need two small metadata tag lines in each song's header in OnSong -
One to listen out in OnSong for Registration changes made on the Genos/Tyros etc, (which sends the song's Program Change Number to OnSong) and the other to send the data from a song selection change made in OnSong, to the Genos, for it to switch to the right Registration.
There are a number of little trip-ups along the way which can catch you out, but basically it is then very quick and easy to copy and and paste these two small lines into a new Chord & Lyrics song page or Score, then to alter the numbers, to quickly setup and link a good sized OnSong library and Set Lists.
The OnSong Consol on PC makes this extremely easy to do from the PC rather than the ipad.
On the Genos to add a new song midi file, I just load up any other songs' midi file, and change the PC number with the dial and resave the new file with the new song name.
I got halfway through a YouTube video on all this a year or two back, but I am not a YouTube expert and it got put back (as did a similar exercise on the Tyros before that
)
I would have thought it was all relevant to the SX900 but don't know for sure