When people forget the words to a song, they rarely stop singing. They carry on in da-da-da and hmm-mm, and the nonsense lands exactly where the words used to be: the right number of syllables, the stress in the right place, a breath where the line breaks. Whatever let go of the words kept hold of the shape they were poured into. It is like the clean square left on the wallpaper where a picture used to hang, except that you can sing the square.