John Prine's latest album teams the ace songwriter with country music's finest gals on a collection of classic duets. Helping him promote the Grammy-nominated In Spite of Ourselves, Iris DeMent will join Prine for a special one hour edition of PBS' Sessions at West 54th on Jan. 28 and Emmylou Harris will swap vocals with Prine on CBS' The Late Show with David Letterman on Jan. 31. Incidentally, The New Yorker named In Spite of Ourselves their No. 1 album of 1999.