You can do this all in the File.open block:
Dir.chdir 'C:/Users/name/Music'music = Dir['C:/Users/name/Music/*.{mp3, MP3}']puts 'what would you like to call the playlist?'playlist_name = gets.chomp + '.m3u'File.open playlist_name, 'w' do |f| music.each do |z| f.puts z endend