Michael Finnissy is Mr. Complexity, whose crunchy five-hour piano cycle The History of Photography in Sound was reviewed in Gramophone’s January issue. But this disc reveals another side of Finnissy. His Grieg Quintettsatz is a compassionately composed love letter in sound to Edward Grieg, written Finnissy says ‘for fun’- shortly after his stylistically faithful completion of the Piano Quintet in B flat major which Grieg put to one side as he began to revise Peer Gynt in 1892. Grieg would never touch his sketches again; Finnissy picked them up in 2007 and both projects were complete by 2012.

It’s unlikely that Finnissy will become known as the composer of Grieg’s Piano Quintet in the same way that Anthony Payne is the composer of Elgar’s Third Symphony. Each note could, in theory, have been etched by Grieg’s own pen, but I doubt whether he would have shaped them into this unbroken 30-minute structure. Finnissy keeps an objective distance from the material at the same time as being utterly immersed within it. Describing the resulting sonic capriccio as a ‘Kammersymphonie’, Finnissy’s dimensions project these abandoned relics into the future; Schoenberg, yes, but also Bruckner, Wagner and Mahler.

I’ve written before about Finnissy’s canny knack of devising miniatures that just happen to last 30 minutes, and hearing him work that same trick under the guise of another composer is indeed attention-grabbing. Even with my workaday knowledge of his music, I can hear just how fertile the potential of this material must feel to a confirmed Grieg aficionado; and, harmonic muscles flexed, Finnissy takes it on a power workout, his structure ambling urgently towards a folksy, cascading scherzo and an introspective, wistful slow movement, both invented, before a recapitulation of Grieg’s original material.

The Kreutzer Quartet and pianist Roderick Chadwick play the game, an authentic mode of 19 th -century expression that refuses to acknowledge its genuine fakeness; but in Grieg Quintettsarz you’re just waiting for that moment of stylish slippage, for Finnissy not just to protect but to take this material into the modern world. Progress is glacial; but all of a sudden you glance back and realize you’re in another gestural world, a world of distorted scale and far-flung harmonies informed, Finnissy tells us, by John Cage and David Hockney.

—Philip Clark