Throughout his life Schubert was drawn to the piano duet more than any other great composer, partly for practical reasons (there was an insatiable demand for four-hand music in Biedermeier Vienna), partly because he evidently relished the rich, quasi-orchestral sonorities that two players could conjure from one keyboard. In the late 1970s Christoph Eschenbach and Justus Frantz recorded around half of Schubert’s four-hand output. Their performances were always unsurpassed for refinement of touch and hyper-sensitive balancing of voices. Reincarnated in a slimline four-CD set they make a terrific bargain.

Even they cannot do much for dull utility pieces like the three Marches héroïques. But with playing that mingles fire, grace and a vast range of colour and dynamics (finely caught by the engineers), they rekindle the appetite for the Marches militaires, so much more appealing as piano duets than in their more familiar brash orchestral guise. The magnificent Grand Duo (which Schumann, Joachim and others took to be a blueprint for a symphony) is dangerously leisurely and flexible in its opening movement. Both rival performances listed strike a better balance between epic sweep and ravishing detail and give the Scherzo more of Schubert’s prescribed vivace – though Eschenbach and Frantz yield to no one in pace and temperament in the Hungarian-tinged finale.

Among the other masterpieces, the A minor Lebensstürme receives a thrilling, richly imagined performance, with pp and ppp playing of ethereal tenderness, while the F minor Fantasie has drama, colour and intense, aching cantabile, and surpasses rivals in the élan and delicatezza of the Scherzo. A spellbinding performance, crowning a feast of memorable Schubert playing from one of the great duo partnerships.