There is a program available on Ubuntu youtube-dl, that can download videos from youtube.com or other video platforms. But it stores the file in mp4, since it contains video. But sometimes you do not want the video and only the audio. To extract only the audio part, you can use the pacpl comamnd line tool.
Use "Sound Converter" Application for simple conversion
Usage:
$ youtube-dl -f mp4 --output "yourfilename.%(ext)s" https://youtu.be/your-link-here
$ youtube-dl --extract-audio --audio-format mp3 --audio-quality 256 --output "yourfilename.%(ext)s" https://youtu.be/your-link-here
Older Method:
pacpl --to mp3 -v -r -bitrate 256 targetfile.mp4
Ubuntu Software: EasyTAG to modify MP3 MetaData
Update MP3 tags with the command line:
$ sudo apt-get install id3v2
Some useful commands
List all of the tags or specific for a particular file without wild card
$ id3v2 -l *.mp3
Example of how to update title, album, year
$ id3v2 -t "My Title" file-to-update.mp3
$ id3v2 -a "My Album"
$ id3v2 -y 2016