A "midi" (Musical Instrument Digital Interface) file is a kind of music file which has a very quick loading time but the music will sound different depending on what kind of sound card you have. Normally, clicking on the link will start the music. Alternatively, you can save the file to your hard-drive and open it up in windows Media Player (right-click the link and select "save target as"). The midi format is also supported by the latest versions of Winamp. If you have a Macintosh, then Quicktime is the thing to use, although sometimes it may need to go through a kind of conversion process first. If you are listening to midi files through a browser, then you may benefit from a Crescendo or Quicktime plugin.