A few years ago, I was wandering around London after work looking for something to do, when I stumbled upon the Royal Academy of Music's beautiful museum. An exhibition featuring some of the museum's older collections was on display, including a gorgeous little 'crab canon'. I'd heard of them before, knew some of Bach's and saw another when I was studying at university, but I'd never seen such a complete little piece. This one was not just a crab canon (a piece in which the musical material can be played alongside a reversal or retrograde of itself) but was also a full table canon for which the whole page could be turned by 180 degrees and the piece would sound just the same! I otherwise half-remember only that it was in G major and 3/4 time.
I forgot about it for a while but had an excuse to revisit it earlier this year, as I wanted to write something as a little leaving present for an ex-colleague. Thinking a bit more about an inverse crab canon, I wanted to write something where the viewer would quite simply not know which way round it should be held - that it would be identical if turned upside down. This required devising some new rotational-symmetry clefs and recognising that the only dynamic markings could be multiples of forte with hairpins, stems, noteheads etc. all placed as symmetrically as possible. Piano Prelude No.9 'Golden-clawed Inverse Crab Canon' is the result