I wish to redirect a damaged filename 'artist_-title' to 'artist-_title.zip'. I attempted this inshtaccess:

RedirectMatch 301 artist_-_title artist_-_title.zip

I believe I actually do know very well what causes the loop, but I'm not sure much about regular expressions.

You need to write something similar to this:

RedirectMatch 301 artist_-_title$ artist_-_title.zip