With his performances and recordings of the Goldberg and Diabelli Variations, and of Frederic Rzewski’s The People United Will Never Be Defeated!, Igor Levit has already signalled his fascination with monumental works. But even he has never before tackled anything on the scale of Ronald Stevenson’s Passacaglia on DSCH, which is often claimed to be one of the longest single-movement works in the solo piano repertoire.

Stevenson, who died four years ago, was one of the most rewarding of the maverick composers scattered through 20th-century British music. He was a hugely prolific, unpredictably protean figure, and in many ways a latter-day heir to such composer-pianists as Liszt, Alkan and Busoni. That’s the tradition celebrated in the Passacaglia on DSCH, which Stevenson composed between 1960 and 1963 and which is regarded as his defining masterpiece.

Built over the four-note German musical “spelling” of Dmitri Shostakovich’s name (D, E flat, C and B), it’s a vast work – 85 minutes in Levit’s performance – of teeming musical diversity. The three parts take in a baroque suite, three sets of variations and a climactic triple fugue, as well as character pieces such as waltz, pibroch, fandango and symphonic march. The writing is by turns intricately contrapuntal and massively chordal, often densely chromatic but never cutting all its ties with tonality.

The passacaglia is also phenomenally taxing to play, testing pianists’ sheer stamina, as well as their musical concentration and virtuosity, to the limit. Though it has been recorded half a dozen times, opportunities to hear it live are very rare. But Levit’s performance was astonishingly, heroically committed, never flinching from the massive climaxes or reining back the flights of transcendent virtuosity, and making every detail as lucid as Stevenson’s manic invention will allow. It’s hard to imagine this extraordinary work has ever been played better.