Armed and dangerous – two casualties of Soviet-era censorship triumphantly reunited. The lost Prologue to the discarded three-act opera Orango comes rip-roaringly off the surviving piano score in Gerard McBurney’s spookily authentic orchestration. There’s one sensational number (recycled from the industrial ballet The Bolt – another censorship casualty) which culminates in a rampant chorus-line of army and navy generals set against the shock and awe of their assorted weaponry illuminating the night sky. The brutal timpani ostinato finds a darker purpose in the Eighth Symphony, just as that seemingly innocuous ticking percussion motif from the middle movement of the Fourth Symphony has the last laugh in the closing moments of the Fifteenth Symphony.

Orango – the heavily loaded tale of a humanoid ape turning anti-Communist newspaper baron – was the kind of coruscating satire that even the apish Soviet authorities could see through. The surviving Prologue crosses the language of filmic propaganda (an overture of drum rolls, fanfares and one aspiring theme) with Shostakovich’s already well-developed sense of grotesque irony. The ministry of funny falsettos is much in evidence, as are those anarchic gallops, leaving one breathless in anticipation of what might have come next. Esa-Pekka Salonen, like us, can only hazard a guess.

Salonen then turns his penetrating musical intellect on the extraordinary Fourth Symphony, achieving the kind of skewed logic that some merely hint at. It’s a ‘composerly’ account in which every thematic connection, however oblique, has something to say. Clarity is forensic, with the Los Angeles Philharmonic achieving levels of precision that can – in that scarifying string fugue from the first movement, for instance – totally suspend disbelief. And rarely has the enormous final chapter of the piece achieved a more harrowing inevitability. That last great tutti, where triumphalism disintegrates into dissonance, is as close to a musical prediction of the impending holocaust as it’s possible to imagine. As Peter Sellars suggests in his booklet-notes: it’s Mahler’s Second without the Resurrection.