be aware that the binding system has changed in version 4100. This is what produces the file format incompatibility with previous versions. However, when you load a file using the old format into C4 >4100, a backup should be automatically created. I will paste down below an excerpt from this thread:
Excerpt:
Updating
When you load a song or rack file from an older build, Cantabile will automatically upgrade and convert all existing bindings to the new system. Your old song and rack files should continue to work in the new build as before.
IMPORTANT: Any song or rack files saved by this build, either by explicitly saving or automatic saving of racks will not load in previous builds. Before using this build, please back up your current song and rack files.
If you need to go back to an earlier build, you’ll need your old song and rack files.
(Actually, Cantabile will automatically save a backup copy of any song/rack before it overwrites it with a .pre4100 extension appended… but don’t rely on this and it’s better to be safe than sorry).
Gabriel