music_tags.rb

# gem "taglib-ruby"

require 'taglib'
require 'fileutils'

folder = "/Users/aurelian/Music/The Gathering/2007 - A Noise Severe"

Dir["#{folder}/**/**"].each do | alot |

  TagLib::FileRef.open(alot) do | file |
    unless file.null?
      tag = file.tag

      new_name = sprintf("#{folder}/%02d %s.m4a", tag.track, tag.title)
      puts "#{alot}\n\t => #{new_name}"
      FileUtils.mv alot, new_name
    end
  end
end