This month's free MP3 is a bootleg live version of a bootleg track from the unreleased BASEMENT TAPES sessions, "ROCK SALT AND NAILS!" just click on the "DOWNLOAD" link below in the main navigation.
Mac and Safari users can save the file right from their browsers by choosing "File/Save As". PC users should be able to save the file through their media player... if problematic try downloading and using iTunes for PC.