While using Cantabile 4 (build 4338) I made the following two observations:
After switching to another set list, initially no song is selected. I expected that the first song is selected. You need to select a song manually. When you quit and restart Cantabile the first song is selected.
After switching between songs, no media player/ media file is selected. In the routing diagram at the bottom there is the (no selection) indication. I expected that the first media player / first media file is selected. You need to select the media player and media file manually. Even after quitting and restarting Cantabile no selection is made.
Is this behaviour by design? What are your expectations?
Go to Tools/Options then this. Note that if you want to check the “Reload last setlist” you should first select another song load option, check it, then select Load first song in setlist. BTW this screenshot is from an older version of C4 but the menu is pretty similar.