[Zubersoft]

This has to do with how MobileSheets determines what is the "active" song. In the two page display mode, it uses the left page to determine what the current song is. By default, the audio player will only show audio tracks for the current song. You can change this though - tap the settings icon at the top right and then change the track list dropdown to "All tracks in setlist". You should also uncheck "Switch track when song changes". You can then load tracks from any song in the setlist, but you'll have to manually switch tracks. 

Mike