Hello Macramole
Thanks for your reply. I ran a test on a set of short audio clips and made sure the file names and folder name have no special characters in them.

I'm actually on Mac, but I thought to eliminate the small chance of an issue. I still get the same error message.
Any other ideas of what I should do if I want to use other kinds of feature extraction other than STFT? If I tick the other boxes, I get the error as on the first post:

Cheers
Jolon