The programme read a little like a musical version of Kim's Game: not one but two full-scale symphonies, the same number of prefatory pieces, and then a piano concerto to boot: a test for the audience as well as the orchestra. The principal connexion between the works – apart from their contemporaneity – was the celebrated conductor, Serge Koussevitsky. Not only had he premièred Bax's Second Symphony and Prokofiev's Fourth (which he also commissioned), he was a keen champion of Copland's music too. (Indeed, Koussevitsky commissioned Copland's Third Symphony, which incorporates his Fanfare for the Common Man.) Barber's Adagio for Strings is also the result of a conductor's encouragement, this time following the suggestion of Arturo Toscanini to orchestrate the slow movement of his string quartet as a concert item. It was the Bartók then that was a little out of place, in terms of the programming at least, installed rather to complete this year's cycle of his piano concertos in the Proms.

However it was also the Bartók that stole the show. Making her Proms début, the Chinese pianist, Yuja Wang, invested brilliant energy and musicianship in order to make this work fly. Bartók's percussive devices allowed her to demonstrate her consummate command of the keyboard: dazzling repeated notes, never met with that unfortunate, blunted sound of a mismanaged piano; a tone that carried through even the most cacophonous of the pseudo-Baroque textures; and the bravery to have the score on the music desk in front of her.

The most familiar works on the bill – Copland's Fanfare and Barber's Adagio – found the RPO at their most comfortable. The Copland was impressively confident and cleanly executed, whilst the Barber, at times, became a little over-exuberant, unsettling the only real opportunity for subtlety in the programme.

And, just as two wrongs don't make a right, two mediocre symphonies don't make a good one. Bax's was written when he was, in his words, 'going through absolute hell'. And it sounds like it. It's a demanding listen, and, coupled with Prokofiev's slightly aimless work, asked too much by way of concentration. This was a shame for, had only one of these works been included, fatigue wouldn't have prevented the best being found in either symphony. And we'd have wanted more. As it was, when the third hour struck of this musical marathon, it was hard not to focus on the negative, commendable as the performances might have been.

Amazingly, there was never a moment where the orchestra sounded tired. The RPO possesses a distinctive sound, particularly its string section, whose glossy timbre is plushly alluring. But neither is that to say that these waters didn't run deep; there was playing of great intensity, always directed and shaped with authority and vigour by Litton.

In short, if the RPO had wanted more airtime, they should have been asked back for another night instead of overloading one concert. We would have certainly listened.