Within Google Drive there's a shared drive which I can use to get to my music.
I can't find the Shared Drive in the import function in MobileSheets Pro.
How can I sync / download from the Shared Drive?
I don't currently support switching the active drive in the Google Drive integration (although you can go to Settings->Storage->Switch Google Drive Account to switch accounts). Shared folders work fine though, so if you can switch to using a shared folder, that would get you past this problem. I do plan on eventually adding support for switching between different drives, but this would require Google Drive specific UI elements to be added and a lot of modified code. If you use Import->System File Browser and then select the Google Drive app, does that give you a way to access the shared drive? That may be a workaround for you.
Mike