Look at the following code: 
import os
import argparse
from mutagen.easyid3 import EasyID3
from mutagen.id3 import ID3, error

def process_mp3_files(inbox_directory, library_directory):
    for root, _, files in os.walk(inbox_directory):
        for file in files:
            if file.lower().endswith('.mp3'):
                file_path = os.path.join(root, file)
                try:
                    audio = EasyID3(file_path)
                    if 'artist' in audio:
                        artists = audio['artist'][0].split('/')
                        if artists:
                            artist = artists[0].strip()
                            original_artist = artist
                            audio['artist'] = artist
                            
                            # Check library for matching artist
                            library_artist = check_library_casing(library_directory, artist)
                            if library_artist != artist:
                                audio['artist'] = library_artist
                                print(f"Updated artist casing for file: {file_path}")
                                print(f"  Old: {artist}")
                                print(f"  New: {library_artist}")
                            
                            # Update Album Artist if it differs only in casing
                            if 'albumartist' in audio:
                                album_artist = audio['albumartist'][0]
                                if album_artist.lower() == original_artist.lower():
                                    audio['albumartist'] = library_artist
                                    print(f"Updated album artist casing for file: {file_path}")
                                    print(f"  Old: {album_artist}")
                                    print(f"  New: {library_artist}")
                            
                            if 'album' in audio:
                                album = audio['album'][0]
                                original_album = album
                                # Check library for matching album
                                library_album = check_library_casing(os.path.join(library_directory, library_artist), album)
                                if library_album != album:
                                    audio['album'] = library_album
                                    print(f"Updated album casing for file: {file_path}")
                                    print(f"  Old: {album}")
                                    print(f"  New: {library_album}")
                            
                            audio.save()
                        else:
                            print(f"No valid artist information found in: {file_path}")
                    else:
                        print(f"No artist information found in: {file_path}")
                except error as e:
                    print(f"Error processing file {file_path}: {e}")

def check_library_casing(directory, name):
    for item in os.listdir(directory):
        if item.lower() == name.lower():
            return item
    return name

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Process MP3 files to update artist metadata and match library casing.")
    parser.add_argument('inbox', type=str, help="The directory containing MP3 files to process.")
    parser.add_argument('library', type=str, help="The library directory with artist/album structure.")
    args = parser.parse_args()
    
    process_mp3_files(args.inbox, args.library)

Change the code to make the matching between the mp3 metadata and the library folder more fuzzy. Example: MP3 Artist: "Fred again." Folder Name "Fred again._" This should be detected and the MP3 Artist should be modified according to the folder name.