I have an alias setup in my .bash_profile to easily download and save as .mp3 file:
> alias ymp3="youtube-dl --extract-audio --audio-format mp3"
> alias ymp3="youtube-dl --extract-audio --audio-format mp3"
alias mp3='youtube-dl -x --audio-format "mp3" --audio-quality 0 --embed-thumbnail $*'
ytdl()
{
mkdir /tmp/ytdl && cd /tmp/ytdl
for URL in "$@" ; do youtube-dl -o '%(title)s.%(ext)s' "$URL" --restrict-filenames; done ;
mv /tmp/ytdl/* ~/Desktop/
rm -rf /tmp/ytdl
exit
}e.g. youtube-dl -f 140 "$URL"