Converting all flacs and copying all meta. All folders & files are mirrored including images. Run like this `python drop-the-bytes-music.py "D:\Library\Music" "D:\Library\PhoneMusic" -v -j 4`

drop-the-bytes-music.py

import argparse

from mutagen import File
from mutagen.flac import FLAC
from mutagen.easyid3 import EasyID3
import os
import shutil
from subprocess import call
from multiprocessing import Pool

from mutagen.id3 import ID3NoHeaderError


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('source_dir', metavar='source_dir', type=str, help='Path to a directory full of flacs.')
    parser.add_argument('dest_dir', metavar='dest_dir', type=str, help='Path where you want your mp3\'s to be dropped.')
    parser.add_argument('-j', '--threads', type=int, default=os.cpu_count(), help='How much threads do you want to run.')
    parser.add_argument('-v', '--verbose', action="store_true", help='Display the resulting set of tags when done.')
    args = parser.parse_args()
    sync_folder(args.source_dir, args.dest_dir, args.threads, args.verbose)


def sync_folder(source, destination, verbose=False, threads=os.cpu_count(), level=0):
    if not os.path.exists(destination): os.makedirs(destination, exist_ok=True)
    files = os.listdir(source)
    convert_queue = []

    for file in files:
        file_source = os.path.join(source, file)
        file_dest = os.path.join(destination, file)
        if os.path.exists(file_dest) and not os.path.isdir(file_source):
            if verbose: print(('\t' * level) + f'File: {file} already exists. Skipping')
            continue

        if os.path.isdir(file_source):
            if verbose: print(('\t' * level) + f'Syncing folder: {file}')
            sync_folder(file_source, file_dest, verbose, threads, level + 1)
        elif file_source.endswith('.flac'):
            pre, ext = os.path.splitext(file_dest)
            file_dest = pre + '.mp3'
            if os.path.exists(file_dest): continue

            if verbose: print(('\t' * level) + f'Converting file: {file}')
            convert_queue.append(tuple([file_source, file_dest]))
        else:
            if verbose: print(('\t' * level) + f'Copying file: {file}')
            shutil.copy2(file_source, file_dest)

    if verbose: print(('\t' * level) + f'Starting convert jobs:')
    pool = Pool(threads)
    pool.starmap(convert_flac, convert_queue)


def convert_flac(source, destination):
    try:
        call(f'flac --silent --decode --stdout "{source}" | lame --quiet --preset extreme - "{destination}"', shell=True)
        copy_id3(source, destination)
    except Exception as e: print(f'Failed converting: {source}')


def copy_id3(srcname, destname, verbose=False):
    try:
        meta = EasyID3(destname)
    except ID3NoHeaderError:
        meta = File(destname, easy=True)
        meta.add_tags()
        meta.save()

    src = FLAC(srcname)
    dest = EasyID3(destname)

    for tag in src:
        if tag in EasyID3.valid_keys.keys(): dest[tag] = src[tag]
    dest.save()
    if verbose:
        print("Copied ID3 tags from %(srcname)r to %(destname)r--result:" % locals())
        print(dest.pprint())


if __name__ == "__main__":
    main()

python drop-the-bytes-music.py "D:\Library\Music" "D:\Library\PhoneMusic" -v -j 4
Source Destination Verbose ThreadCount

FLAC and LAME are required btw