In order to use this script, you need to do certain things in advance –

1. Download youtube-dl, a script which allows you to download videos

https://github.com/rg3/youtube-dl

2. Install ffmpet: an audio/video conversion tool.
Ubuntu users can run the following commands –

  apt-get install ffmpeg libavcodec-extra-53

Note: More details can be found here.

Usage Example: –

 ./musicdownloader.sh http://www.youtube.com/watch?v=8tHu-OwzwPg BereketMengstead-mizerey.mp3

#!/bin/bash

downloader=`which youtube-dl`
ffmpeg=`which ffmpeg`
bitrate=192000

ARGC=$#
LINK=$1
FILENAME=$2
SAVEDFILE=$(basename $0)_mymusic123.mp4

if [ $ARGC -ne 2 ]; then
  echo "Usage: $(basename $0) url-link output-file"
  echo "Example: $(basename  $0)  http://www.youtube.com/watch?v=fQZNiMckKbI Azmari-ethio01.mp3"
  exit
fi

$downloader -f 18 $LINK -o $SAVEDFILE  &&  $ffmpeg -i $SAVEDFILE -f mp3 -ab $bitrate -vn $FILENAME

if [ $? -eq 0 ];
then
 echo "File saved in " $FILENAME
 rm $SAVEDFILE
fi