Brief Analysis A, Jerry Gray and Eddie de Lange's "A string of Pearls":
Qualities for each chord: m.11- I+6
m. 12- II7, flatII+flat7, I+7
m. 13- IV, IV65
m. 14- I+6
m. V7, I+6
It seems that in measures 11-13, each chord is ascending through means of a chromatic sequence until we reach m.13 and move to the IV. The bflat would want to move to keep moving down chromatically, but instead goes up to a c natural which feels awkward since the harmony just went cflat, bflat, you would want to keep moving down two more half steps, but you get that Aflat chord which acts as more of a dominant function since there were two chords built on D and Dflat, even with the interrupting tonic, the Aflat still comes across with a little dominant feel until the fourth beat.