The two columns in this puzzle consist of pieces selected from two sets of works. Those in the left (Sacred) column are the first minutes of some sacred cantatas by Bach. Those in the right (Profane) column are descriptions of English ballad texts. Each of these sets are canonically numbered, Bach works by the BWV catalog, and ballads by Francis Child's "The English and Scottish Popular Ballads." The works are to be paired by index number.
The Bach pieces are:
And the ballads are: (titles as given in Child)
Following the instructions and applying the indices to the titles from the opposite columns produces 10 letters. When read out in ascending index order (Bach, then Child), they read DEBAUCHERY, which is the answer.
2006 MIT Mystery Hunt