Instal libav-tools

sudo apt-get update
sudo apt-get install libav-tools

Install youtube-dl

sudo curl -L https://yt-dl.org/downloads/latest/youtube-dl -o /usr/local/bin/youtube-dl
sudo chmod a+rx /usr/local/bin/youtube-dl

Download mp3

youtube-dl --extract-audio --audio-format mp3 --audio-quality 0 -o '%(title)s.%(ext)s' https://www.youtube.com/watch?v=ID

–audio-quality 0 means the best quality available
-o ‘%(title)s.%(ext)s’ will remove the ID from the filename

Download the file from a web browser (optional if you don’t have FTP, SFTP, are on a Windows bashless box)

For python bellow the version 3

python -m SimpleHTTPServer

For python 3 or higher

python3 -m http.server

Now just browse to http://your-server-IP:8000 and download the file