Create a new version of paste:

import os
import argparse
from itertools import takewhile
import xml.etree.cElementTree as ET

output_dir = os.path.abspath('outputs')
first_attribute_id = 'WaveFile'
second_attribute_id = 'WaveFile2'
category_attribute_id = 'Category'
tags_attribute_id = 'Tags'

def files(path):
    for file in os.listdir(path):
        if os.path.isfile(os.path.join(path, file)):
            yield file

def is_musicfile(file):
    (_, extension) = os.path.splitext(file)
    return extension == '.wav'

def get_filename(file):
    (filename, _) = os.path.splitext(file)
    return filename

def replace_after_last_seperator(seperator, old_string, new_part):
    head, sep, _tail = old_string.rpartition(seperator)
    return head + sep + new_part

def parse_category(file):
    is_alphanumeric = lambda c: c.isalnum()
    return ''.join(takewhile(is_alphanumeric, file))
    
def parse_tags(file):
    # Throw away extension, since it is not included in tag
    filename = get_filename(file)
    # Remove category from file and'index' (A or B) from file, as they are not included in tag.
    category = parse_category(filename)
    invalid = lambda tag: (tag == category) or (tag == 'A') or (tag == 'B')
    tags = [tag.strip().rstrip('s') for tag in filename.split('-') if not invalid(tag.strip())]
    return tags

def create_preset_file(xml_file_root, file_a, file_b):
    # Modify STATE tag
    for state in xml_file_root.iter("STATE"):
        # Get current text from sought after fields in STATE tag
        wavefile1 = state.get(first_attribute_id)
        wavefile2 = state.get(second_attribute_id)
        # Create new strings to replace template strings in STATE tag
        new_first_attribute = replace_after_last_seperator('\\', wavefile1, file_a)
        new_second_attribute = replace_after_last_seperator('\\', wavefile2, file_b)
        # Write changes to XML tree
        state.set(first_attribute_id, new_first_attribute)
        state.set(second_attribute_id, new_second_attribute)
    
    # Modify Category, Tags inside ATTRIBUTES tag
    for attribute in xml_file_root.iter('ATTRIBUTES'):
        # Parse new Category and Tags from input file
        new_category = parse_category(file_a)
        new_tags = parse_tags(file_a)
        # Write changes to XML tree
        attribute.set(category_attribute_id, new_category)
        attribute.set(tags_attribute_id, ' '.join(new_tags))
     
# Main logic below ->
# Create output folder if it does not exist
if not os.path.exists(output_dir):
    os.makedirs(output_dir)

# Parse alternative template file
parser = argparse.ArgumentParser()
parser.add_argument(dest='template', help='path to template xml', nargs='?', default='template.xml')
args = parser.parse_args()
template_file = args.template

# Read and partition music files to work on
musicfiles_in_dir = [file for file in files('.') if is_musicfile(file)]
a_files = [file for file in musicfiles_in_dir if 'A' in file]
b_files = [file for file in musicfiles_in_dir if 'B' in file] 
musicfile_pairs = [(file_a, file_b) for file_a in a_files for file_b in b_files if file_b.replace('B', 'A') == file_a]

# Create xml files for every pair of music files
for (file_a, file_b) in musicfile_pairs:
    # Parse template file and create editable root element
    template_document = ET.parse(template_file)
    template_document_root = template_document.getroot()
    # Create new preset file
    new_preset_file = create_preset_file(template_document_root, file_a, file_b)
    # Write changes
    output_file = f'{get_filename(file_a)}-and-{get_filename(file_b)}.xml'
    write_path = os.path.join(output_dir, output_file)
    template_document.write(write_path)

print(f'Done! Result can be found at {output_dir}')