Thanks, I think it must be something like that, but I have downloaded files that appear within synthesia but I can’t find them in the files app ! I have found synthesia in files manager but it only has 1 midi in it .
I noticed recently that the "Inbox" folder seems to be hidden for some reason in the Files app. If you use the older style method of getting the files out by connecting to any computer with iTunes (or just a Mac running macOS Catalina or later), you can get the Inbox folder that way, which should have the rest of the missing songs.