Merry Christmas! You can try https://colaku.com/~tomsk/c64tapwav/ (there is a readmefile in the zip explaining.. Maybe that works better for you?
Merry Christmas! Thank you for your suggestion. I will have to wait until I have access to a Windows machine, since these days I am running Linux almost exclusively. The readme file does not actually describe all the dependencies as it turns out. So there might be obstacles on the way. But thank you anyway for the suggestion.
I have tried c64tapedecode https://github.com/lunderhage/c64tapedecode
It produced a TAP file but it didn't work completely, at least not in VICE. The second loading screen of the girl with the city scape and the music comes up but then VICE locks up with a CPU jam. It's a bit disappointing. But the music on the album is very good. I like the album for that.
Is your program doing anything special that makes it unrunnable on an emulator? I will then have to wait until I have access to real hardware.
I tried again with a new WAV file generated with CDex. The results are "better" in a way. Now the picture of the second load screen looks much cleaner (some corruption on the lower edge) but the music is completely garbled.
At least the game seems to start but I'm still not entirely happy. I didn't expect this to be such a delicate process.
I'm always happy about any pointers as to what I could try. Maybe it will even help other people. Thank you.