Hello......I haven't used the songbook, but if you are playing a midi file type song you really aren't using the styles that are in the memories, but rather a sequence of a song. If these are indeed recorded styles that were played live, then recorded, you might be able to retain these settings. After you play one of these songbook songs press the VOICE button and see if the voice shown was what you were hearing. Do the same with the STYLE button. If these are both showing the voices and style of the song you just played you can save this setup in one of the 16 registration memories. Try this and see if it works. Good luck.
P.S. I love the Music Data Base settings. Try tweaking the ones you like and save those in the registration memories.