BBCSO, Mälkki, Barbican Hall

Fashionable concertgoers, if you'll forgive the oxymoron, may have missed the raciest heartbeat of a dizzying week. While Barenboim's Beethoven and Vänskä's Sibelius packed in the cognoscenti at the Royal Festival Hall, kids tagging along to the BBC Symphony Orchestra's "Family Music Intro" and a hardcore of rare-repertoire collectors at the Barbican were treated to a parade of oddball scores dazzlingly communicated by another of those amazing Finnish conductors, Susanna Mälkki, and Portuguese pianist Artur Pizarro.

Make no mistake, these are dense programmes the BBC insists on offering, not overly long in terms of duration but leaving the players, and sometimes the audience, wilting from one work too many. Last night we, at least, came out charged with fresh energy. Interestingly the last time I heard one of those insanely complex scores by postwar German modernist Bernd Alois Zimmermann, represented last night by his "prelude for large orchestra" Photoptosis, Vladimir Jurowski had made it all add up by starting his three-parter with Debussy's Jeux and Mozart, both quoted by Zimmermann, and followed up his use of the Veni, creator spiritus plainsong, a regular visitor, with a parallel chorale in Brahms's First Symphony.

There were no such obvious connections yesterday: the works Zimmermann jams into the central college of Photoptosis are by composers not featured elsewhere in the concert: Beethoven, Scriabin, Wagner, Tchaikovsky and Bach. Yet you'd have needed x-ray ears, so to speak, to sift out trumpeting Parsifal or the Sugar Plum Fairy from the dreamlike textures. They're merely ghost players in the creative mirror of whitening light suggested by the slightly pretentious title. This is an orchestral landscape which can sound curiously arid in recordings yet which here had an underlying vibrancy even before it reached its final jungle of exuberant noises. The players looked terrified but sounded glorious as Mälkki, beating one in each bar as clearly as she could, guided them through the labyrinth to set the whole hall glowing with orchestral colour.

The children in the audience went along with this, I think; less so the griefstricken variations above a ground bass of Webern's first major opus, his Passacaglia. Yet even here Mälkki cut like a knife through lavish outbursts in a way that Barenboim never had the previous evening in Schoenberg's more melodically memorable Pelleas und Melisande.

The rest was sheer pleasure mixed with a dash of terror. It's always a spectacle to see a pianist keep his right hand still while the left runs the crazy gamut of the keyboard in Ravel's heady concerto written for the one-armed pianist Paul Wittgenstein, wealthy brother of Ludwig. Pizarro thundered clearly in the lower reaches of his Yamaha grand - the instrument sounds muddier in the middle register - and carried off the feat of creating one colour for the melodic line and another for the support. He seemed to be enjoying every minute of Mälkki's charismatic support, spacious in the stately dance and making sure the rhythmic tattoos of the jazzy-grotesque central march had as much colour as the cool orchestral solos above (full marks, as ever, to trombonist Helen Vollam for projecting the outrageous slides).

Pizarro was very welcome back in the second half for, believe it or not, a piano concerto by Richard Strauss. In fact there are three, and curiously the later Panathenaenzug, also written for Wittgenstein, would have connected even better to the Ravel and shared its passacaglia form with Webern. Instead we got the early Burleske, a witty commentary on the 21-year old Strauss's infatuation with his then-idol Brahms. The timpani's melodic line almost makes it an obbligato instrument, and Mälkki humorously encouraged Christopher Hind to let consummate rip when necessary. PIzarro seemed to lose his way near the beginning, but recovered to sparkle and smile at the Till Eulenspiegelesque turns of phrase. Nor did the work, with its rather dutiful recap, seem for once a minute too long.

The Burleske also celebrates the start of Strauss's love-affair with the waltz. Ravel's La Valse, of course, is something else: a hazy-sensuous impression of a Vienne ballroom in the mid-19th century which tumbles into an expression of its demise. Textures were predictably immaculate from an orchestra on top form, and the later brass bludgeoning truly scary, but what surprised was Mälkki's teasing delight in the homage to the Johann and Josef Strausses, whom Ravel also adored. On the strength of this, the Vienna Philharmonic should sign her up immediately for a future New Year's Day concert. That's not very likely to happen, given the disgracefully low profile of women even within the orchestra, but it should. And if the VPO don't get her, some other great orchestra ought to snap up the brilliant Mälkki as its principal conductor as soon as it can.

Check out what's on in the Barbican Centre this season