As with Schiff’s Schubert Sonatas and Impromptus for ECM New Series (6/19), so his Brahms concertos, self-directed from a restored 1859 Blüthner, serve as a master cleanser of old preconceptions and impressions. This is by no means an antiquarian job – or ‘Brahms lite’, to use Richard Taruskin’s pejorative term in the context of Historically Informed Performance – even if Schiff in his contribution to the booklet notes speaks in the well-worn terms of restoring the composer’s oft-neglected indications and remarks. What he and the OAE offer is not so much to do with authenticity as with freshness and ‘detoxification’, something akin to letting the daylight into Miss Havisham’s room and removing the cobwebs from her wedding cake. We come away realising that ‘Brahmsian’ is no antithesis to transparency, intimacy, tenderness or fragility.

As with switching from processed food to fresh ingredients, it may take a while to adjust to the subtleness of the palate, as indeed of the palette – the unadulterated contours, lines and timbres. Here’s the opportunity to accept and relish the vulnerability of the piano as a valid alternative to confrontational muscularity and limelight-hogging. How touching, for example, in the Adagio of the D minor Concerto (No 1) is the orchestra’s tender consoling of the piano’s quietly anguished confessions, as though each has become a character in a romantic novel. Here and throughout, Schiff sustains singing lines and broad phrasing much more naturally than Hardy Rittner with Werner Ehrhardt (also on period instruments, with an 1854 Érard). Schiff’s finale is also far less choppy, sacrificing little or nothing of the lyricism that was the bedrock of his modern-instrument recording with Solti. Indeed, the rather shallow sound of the piano in that recording in many ways creates a more awkward first impression, especially heard against the powerhouse backing of the Vienna Philharmonic.

The unity of purpose between Schiff and the OAE is as much to do with the compatibility of the instruments as with interpretative intent. The remarkably sumptuous natural horn, fully on display at the ceremonious opening of the B flat Concerto (No 2), is ideally complemented by the delectable stringiness (once you are acclimatised) of Schiff’s historic Blüthner. This is one of those instruments that truly has a personality of its own. The parallel- rather than cross-strung bass favours transparency over resonance, while the ‘Blüthner Patent Action’ (distinct from the more resistant roller action that facilitates repetition) allows for a smoother, lighter touch. This, together with the distinctness of registers, gives the piano a chameleon-like blend with the orchestral timbres and colours, granting it a concertante rather than oppositional role, especially in the symphonic unfolding of the Second Concerto. Here Schiff and the OAE avoid the dichotomy between the twin peaks of the first two movements and the more modest outlines of the last two. The buoyant last movement is for once entirely to scale with the rest of the piece. It would be tempting to associate its flirtatious à l’hongroise moments with Schiff’s own roots, but imaginative affinity is above such clichés.

For all their declared faithfulness to the score, Schiff and his team are not slaves to it. Caprice, pliant rubatos and tasteful portamentos are plentiful, always in the service of nobility, elegance and chamber-like dialogue. Much has been said and written about Brahms’s own flexible attitude to rhythm and tempo. Still, eyebrows may rise at the three-stage broadening for the D major largamente in the second movement of the B flat Concerto (from 5'11"), and the subsequent emergency accelerando. Is this change of gear just to accommodate the slithery double octaves in the piano? Is it artistic licence or perhaps something to do with the limitations of the piano action? Has Schiff discovered something in the composer’s manuscript that the rest of us don’t know about? Whatever the case, this is the only passage that struck me as artistically questionable.

I have tried to find a previous recording of the B flat Concerto on period instruments but without success. ECM makes no claim to being first in the field. Be that as it may, something tells me I will find it hard to go back to modern-instrument performances without a degree of culture shock. Too bad. This is a disc that arrives with great expectations and delivers no less great revelations.