product.rb

# before 
lyrics.each do |lyric|
  rules.each do |rule|
    clip = Clip.new \
             song_path: song_path,
             lyric:     lyric,
             rule:      rule
    arr << clip
  end
end

# after
lyrics.product(rules).each do |l,r|
  clip = Clip.new \
    song_path: song_path, lyric: l, rule: r
  arr << clip
end