The unconscious phenomenon of muscular memory is what enables us humans to become really quite good at impressive co-ordinated feats like playing musical instruments, given enough practice. But it causes difficulties for those of us who then try to teach the instruments to beginners.

I know; I've tried it. You sit there watching the pupil try to wrench their hands around some barre chord or awkward fingering, watching him or her stop and think before each move of the fingers, a painfully slow procedure. And you ask yourself: what on earth did it feel like, all those years ago, to be doing that?

Well, there's an easy way to remind yourself exactly how it felt. Take your instrument of choice and try to play it back to front. If it's a guitar, hold it left-handed (or right-handed); if it's a piano, try to play upside down or cross your hands; if it's woodwind, hold it back to front or upside down; whatever.

Your fingers still fit over the valves/keys/buttons/strings/frets, and you know technically how to produce the sounds you want - but suddenly you've lost all that unconscious, spontaneous muscular memory that has come to guide your fingers after years of practice. Suddenly, you too have to stop and think before each move, calculate where your fingers should go next, and then move them.

It's very illuminating.