Usage:
$ ./ez-youtube-dl.sh https://www.youtube.com/watch?v=yswb4kjm94g
[youtube] yswb4kjm94g: Downloading webpage
[youtube] yswb4kjm94g: Downloading video info webpage
[youtube] yswb4kjm94g: Extracting video information
[youtube] yswb4kjm94g: Downloading MPD manifest
[download] Destination: /Users/hernamesbarbara/data/youtube_dl/Band of Horses - The End's Not Near.f135.mp4
You can then convert it into an mp3 like so:
$ ffmpeg -i Band\ of\ Horses\ -\ The\ End\'s\ Not\ Near.mp4 -vn \
-acodec libmp3lame -ac 2 -qscale:a 4 -ar 48000 \
band-of-horses-the-ends-not-near.mp3