I don't like you people who are downloading a youtube video as mp3. Because you're transcoding lossy to lossy, something that always! Breaks, especially when you encode to the most lossy format of all lossy formats. This is the command line I use to just grab youtube playlists, this is the command line I used to download this one entire channel and organize into playlists etc, and remove the video ID from the filename, also keeping in native audio stream.
youtube-dl -x -o "%(uploader)s/%(playlist_name)s/%(title)s.%(ext)s" URL
also make sure you have ffmpeg and ffprobe, can be found here, in either the same directory as youtube-dl or in your path. I actually put youtube-dl in my path too, so yeah! And if you want to transcode, use --audio-format format after the -x, where most of the formats are their file types except ogg, which is called vorbis. That's because it's using the vorbis codec. The majority of youtube video/audio streams I see are opus and aac, though I see quite a bit of vorbis too. Youtube does not use mp3, so transcoding to mp3 will be nothing but a loss of quality. If you want to do it, download everything formatted as wav and use lame.exe, setting it to something like 192KBPS vbr, that will give you awesome quality. For size, use 160/192KBPS vorbis. But don't encode the vorbis data to vorbis!
An anomaly in the matrix. An error in existence. A being who cannot get inside the goddamn box! A.K.A. Me.