Gemfile

source 'https://rubygems.org'

gem 'hidat-ruby-echonest', git: 'git://github.com/hidat/ruby-echonest.git'
gem 'ruby-graphviz'
gem 'ruby-mp3info'

generate.rb

#!/usr/bin/env ruby

require 'mp3info'
require 'echonest'
require 'graphviz'

API_KEY          =  '' # Echonest API Key
ARTIST_THRESHOLD = 5 # Minimum number of songs required to include an artist.
MUSIC_DIR        = '/home/john/Music'

e = Echonest(API_KEY)

artists = {}
nodes   = {}

g = GraphViz.new(:G, :type => :digraph, :ratio => 'compress')

# this might take a while...
Dir.glob(File.join(MUSIC_DIR, '**', '*')) do |file|
  next unless (file =~ /\.mp3$/i rescue nil)

  Mp3Info.open(file) do |mp3|
    if mp3.tag.artist
      a = mp3.tag.artist.strip.downcase
      artists[a] ||= 0
      artists[a] +=  1
    end
  end

end

total = artists.values.reduce(0){ |a,b| a + b }

artists.each do |name, count|
  next if count < ARTIST_THRESHOLD

  puts "#{name.ljust(32)} #{count}"
  nodes[name] = g.add_nodes(name, {
    :shape => 'circle',
    :size => (count.to_f / total) * 100,
    :style => 'filled',
    :fillcolor => '#3366cc',
    :fontcolor => '#f0f0f0',
    :fontname => 'Ubuntu'
  })

  e.artist(name).similar['artists'].each do |row|
    a = row['name'].downcase.strip
    g.add_edges(nodes[name], nodes[a]) if nodes.has_key?(a) # only include artists in our collection.
  end

end

g.output(:png => 'output-graph.png')