If you haven't done it yet, mark your calendar for May 20. It is the final show for the "Late Show with David Letterman." David Letterman hasn't said who the final musical guest will be, but speculation has centered on Elvis Costello, the Dave Matthews Band or Norah Jones. Emmylou Harris, The Avett Brothers with Brandi Carlile, Mumford and Sons, Ralph Stanley and Amos Lee have also been mentioned.

More will be announced shortly. This week's musical guests will include Chris Stapleton, Iron and Wine, Tracy Chapman and John Mayer as the countdown continues for the finale of "Late Show with David Letterman."