KindChimpanzee37 , I ensured that the dataset_name is the same in get_data.py and preprocessing.py and that seemed to help. Then, I got the error RuntimeError: No audio I/O backend is available. , because of which I installed PySoundFile with pip; that helped. Weirdly enough then, the old id error came back. So, I re-ran get_data.py and then preprocessing.py - this time the id error was gone again. Instead, I got raise TypeError("Invalid file: {0!r}".format(self.name)) TypeError: Invalid file: instead. Going with https://github.com/librosa/librosa/issues/1236#issuecomment-691113323 I got that I need a newer version and because of other posts installed soundfile.

Anyway, I re-ran get_data.py and then preprocessing.py again and now it seems to work.

Takeaway:
Maybe soundfile should be added or updated in the respective script that installs venv?
Further question:
Why do I need to run get_data.py every time right before I run preprocessing.py ? That is very inefficient during debugging. What am I doing wrong here?