Hi, I have Onsong running now with my BB. All working great - I am sending program changes to change patterns and tempos for songs (coming from within the chart in Onsong). My question is…can I change the drum kit, ideally as another MIDI command, from within Onsong? This would help with using, say, a dance kit for a disco tune or something like that. I do a Dueling Pianos gig and this would save some time as you can imagine. If you can help, thanks!
Yes you can. I don’t use OnSong myself but I’ve seen other people using it to send similar MIDI messages to BB 
I’ve also heard that there have been problems with the mentioned midi messages, but I think that was related to the specific OnSong version 
Hello,
I don’t have OnSong, so I’m unable to test this, but generally, you can change drumsets using the following MIDI message:
CC: 116
(Command name: Drumset)
Value: 0-127 (selects a specific drumset)
If you have any further questions, feel free to reach out!