Prom 43: Argerich, West-Eastern Divan Orchestra, Barenboim

It's not so long since Daniel Barenboim sat around a table with Israeli officials telling him that Wagner couldn't be played in the homeland when someone's mobile fanfared the "Ride of the Valkyries", demolishing the opposition's case.

At the opposite end of the scale to all that flash of battle-lust came last night's unexpected first encore to a Wagner second half – the Act Three Prelude to Die Meistersinger von Nürnberg. It foreshadows opera's most humanistic monologue, in which a deep thinking man of the people bewails the folly and delusion which so quickly knock civilization off course – something very familiar to the Middle Eastern players of the West-Eastern Divan Orchestra, and to the Albert Hall audience in recent months, albeit on a less murderous scale.

Barenboim's overall programme planning, three encores included, was unorthodox and typically generous. Assertive major chords began and ended the official programme, though Jörg Widmann in his Con brio leaves the tonal moorings of the symphonies he’s homaging, Beethoven’s Seventh and Eighth, predictably soon. That was already vieux jeu by 2008, when the piece took its first form, and if the questioning Widmann wants is to take a grip, it needs the kind of cohesion and drive he offers in spades on other works – which is not to say that Barenboim and the players didn’t exploit its full vividness.On the last three occasions I’ve heard Martha Argerich, she’s been helping out great colleagues whose fire has now lost some of the focus the 75-year-old still has in spades. Is there any pianist who can run the gamut more brilliantly, or make the playing sound like startling improvisation? Liszt’s First Piano Concerto was in some ways a perfect showcase, from the thundering but still transparent double octaves to the transcendental flights of the scherzo dialogue with the famous triangle solo – the artistic player shared the applause with her – and the brief poetry of the Quasi adagio. Nor was Barenboim’s orchestra in the shade; the opening unisons showed the strings’ dark side to best advantage – it is, overall, a warm mezzo sound – and the woodwind solos against Argerich’s crystalline trills in Liszt's slow movement could hardly have been more beautifully phrased.

Depth there is not, though, not in this work. I’d hoped we might find it in a solo encore of a greater Liszt or Chopin piece. Inevitably, though, the offering – again, extremely generous – was the Schubert Rondo in A major for four hands which we got in last year’s Staatskapelle Berlin visit to the Festival Hall with Argerich as soloist. Barenboim took the upper lines very daintily; the whole came across as either free or too loose in its rhythmic sense, according to taste.

Barenboim’s Wagner half got off to a spectacular start with the Tannhäuser Overture. So often do we hear it with the Venusberg music attached that it was good to be reminded how the original version is perfect ring composition, though with Barenboim getting the players to up the frenzy of the orgy and the majesty of the returning Pilgrims’ Chorus past the dead centre (another fine clarinet solo). His greatest gift is to animate players way beyond the call of duty. That happened here, but less so in the excerpts from Götterdämmerung, perhaps too momentously weighted for the context when they could have taken flight a little more. Still, some of the key changes set the pulses racing, and the heroine giving us Siegfried’s horn call from above the bust of Henry Wood sounded even louder and fuller than she would have done from the orchestra.

Only Barenboim would have chosen the Meistersinger Prelude to conclude, rather than to start, the official proceedings. And why not? The music ends the opera, after all, and this would have been the ultimate gesture of reconciliation for a festive occasion had not the Act Three Prelude given us something more reflective to think about. And then the anticipated send-them-home-exultant second encore, another Act Three Prelude, from Lohengrin: a brilliant preface to a wedding that goes disastrously wrong. Fortunately there are no signs of anything amiss, musically speaking, in the ever-deepening union of the West-Eastern Divan project.

• Listen to this Prom for the next month on the BBC iPlayer
• Read more Proms reviews on theartsdesk