When William of Aquitaine, over a thousand years ago, made a song about dreyt rien -  just nothing -  he ended by sending his own song away; or rather, the song abstracts itself. Like a pleased cat, the last stanza whisks almost but not utterly out of sight. This ending sings its own, enigmatic destination: to be passed on to someone, who will pass it on to someone else somewhere around Poitiers. This last, remote and nameless person might be able to supply la contraclau, the missing companion-key, to unlock the alluring, portable lyric-as-casket. What does this mean? By the point that the song and composer arrive at the notion of going to seek a key, the listener has been coaxed into staying, and has been both teased and satisfied.

You must have seen the look on the faces of people about to read poetry: visor down, determined against being moved in conjunction with the poem, as if tasked with exiting the poem with a bullet-point or two about what it means. Perhaps you have seen a suitcase come off the carousel at the airport, lock intact but a slash in the sides, selected possessions gone?

Often enough, a key is not an instrument of opening. Divorced from its lock, it leaves both its owners, the forged home and the human possessor. Dense with possibility and also with time, into what would it lead, if it could? What was its history (criminal or eager or arthritic) of handling? As an object, it may sadden or tantalise its keepers; but ...