Two pieces of music encapsulate the spirit of Advent for me. One is the plainchant Rorate Caeli and the other is Bach’s Cantata 140, Wachet auf (“Wake, O wake, for night is flying”). Its words are based on the parable of the wise and foolish virgins who hear the watchman’s cry announcing the arrival of the bridegroom at midnight; and its music is based on Philipp Nicolai’s magnificent chorale of 1599. Both pieces in their way give voice to longing, and it is longing which focuses hope and gives it the affective, dynamic quality which makes it radically different to mere optimism.