I am currently using OnSong with my PSR-SX900 connected over a Yamaha MD-BT01 Bluetooth adapter to load registrations on the keyboard or to display songs based on the registration selected on the keyboard, i.e., successful two way Midi communications between OnSong and the keyboard. This will also work for Genos keyboards also.
I am using the latest Midi command method (Midi Sysex) to access the registrations. The Midi Sysex command method is only supported by the Genos and PSR-SX keyboards. The older method (Midi PC/MSB/LSB commands from the PSR and Tyros keyboards) are still supported by the Genos and PSR-SX keyboards but the Midi Sysex command method provides more flexibility in where the registration banks can be stored on the keyboard, more flexibility in how the registration banks can be named and removes many limitations of the older method.
Every time a registration is manually loaded, the keyboard sends out a Midi Sysex command indicating the storage location of the loaded registration bank including the active registration memory button. If that same Midi Sysex command is sent back to the keyboard, the indicated registration will be loaded.
So the goal would be to capture the Midi Sysex command associated with the desired registration issued by the keyboard and assign that Midi Sysex command to the desired song in its Send and Receive Midi metadata sections in OnSong.
Conceptually, Forscore, Mobilesheets and Songbook+ etc. all have to do the same capture and assignment process.
The Send Midi metadata section of a song will send out any Midi commands that are there whenever a song is selected for display in OnSong. The Receive Midi metadata section of a song will trigger that song to be displayed when OnSong receives a Midi command which matches the Midi command in its list. Unfortunately, only the first Midi command in the Receive list will be accepted as the trigger command.
OnSong has a Midi Learn/Listen capability in each of its Send and Receive Midi metada sections which, if enabled, will listen for and capture Midi commands sent to OnSong.
Therefore to capture the Midi Sysex command for a loaded registration, enable Midi Learn/Listen in the song's Send Midi metadata section first and then load the appropriate registration on the keyboard. The keyboard will send the appropriate Midi Sysex command to OnSong which will capture it and assign it to the song's Send Midi metadata section. Now every time that song is displayed in OnSong, the captured Midi Sysex data will be sent back to the keyboard to instruct it to load that registration.
Do the same capture method for the song's Midi Receive metadata, i.e., enable Midi Learn/Listen in the Receive Midi metadata section, load a registration on the keyboard, capture it in OnSong. Make sure that the captured Midi Sysex command is the ONLY one in the list (or at least the first one in the list). Now any time that registration is loaded on the keyboard, OnSong will display the associated song.
Disable the Midi Learn/Listen capability when done.
NOTE: Songbook+ does the above in one step rather than two because Songbook+ has a relationship with Yamaha that allowed them to build this integration into their code specifically for the Genos and PSR-SX keyboards.
Requirements for the use of Midi Sysex commands with registrations:
OnSong at the 2020.7.10 or later release level. This release came out about a month ago. Prior to the 2020.7.10 release level, displaying a song in OnSong could only send a Midi Sysex command to select a registration on the keyboard. Loading a registration on the keyboard first would not trigger OnSong to display a song. OnSong would ignore the incoming Midi Sysex command sent by the keyboard.
Additionally, OnSong at the 2020.7 release level requires your Apple device to be at the IOS/iPadOS 13 level or later, i.e., fairly up-to-date.
And lastly, a working Midi conection between the device and the keyboard whether it's over Bluetooth, Wifi or direct connection. This area is probably the most troublesome especially with some of the changes made recently by Apple re networking. So updating the device to the latest OS levels would be beneficial.
Some more info on the integration between OnSong and the Genos/PSR-SX keyboards can be found here ...
https://www.psrtutorial.com/forum/index.php/topic,44563.0.html