As if imbued with a soul of mercury, this virtuosic work moves rapidly and capriciously between two extremes: a lightning-fast and mischevious space, and a far more lyrical and expressive one. The piece shares some resemblance to a sonata in its use of two contrasting ideas, but it diverges significantly in their treatment. After a brief introduction, the first idea becomes highly unstable – marked by wide leaps, quicksilver changes in dynamics, and a very dry sound world. It is contrasted by a mystical and expressive tune, closely spaced, that is awash in resonance. The ensuing developments – which treat the themes separately – transform each theme into the other, climaxing at a cadenza which puts both ideas together for the first time.

But, like two decrepit salmon – who spend their lives seeking the unique space where they can form a brief but extraordinarily sweet union – the two themes, exhausted by the journey, die together in a bittersweet coda.