for banshee... (public domain, own your risk)

itunes_nfc.rb

# Converts UTF-8-MAC filenames in "iTunes Music Library.xml" to UTF-8
#
# Usage: ruby itunes_nfc.rb iTunes\ Music\ Library.xml > iTunes\ Music\ Library.xml
# License: public domain
#
# own your risk.

require'uri'
xml = ARGF.readlines

r = xml.map do |line|
  next line unless /(\t*)<key>Location<\/key><string>(.*?)<\/string>(\r?\n)/ =~ line
  t, oufn, ret = $1, $2, $3
  ofn = URI.unescape(oufn)
  cfn = ofn.force_encoding("UTF-8-MAC").encode("UTF-8")
  cufn = URI.escape(cfn).gsub(/&%23/,'&#')
  "#{t}<key>Location</key><string>#{cufn}</string>#{ret}"
end

puts r.join