To download a single video or a playlist as mp3
yt-dlp --extract-audio --audio-format mp3 -o "%(title)s.%(ext)s" https://www.youtube.com/etcetcetcetc
yt-dlp playlist
yt-dlp -x --audio-format mp3 --audio-quality 0 --embed-thumbnail --add-metadata --ppa "EmbedThumbnail+ffmpeg_o:-c:v mjpeg -vf crop=\"'if(gt(ih,iw),iw,ih)':'if(gt(iw,ih),ih,iw)'\"" -o "%(title)s.%(ext)s" "PLAYLIST_URL"