Organist Katrina Liao joins us to talk about one of her favorites, this chorale prelude that is crackling with spiritual fire. The off-beat bass at the beginning is a neat touch -- could Bach have meant to signify the Holy Spirit by focusing on the 3rd division of the beat? -- but, Katrina's favorite moment comes in the second verse, when the bass gets to carry the melody with a strong, reedy pedal sound. Christian also points out a hidden "B-A-C-H" motif.