BBC National Orchestra Of Wales, St David's Hall, Cardiff, review So much hangs on a new principal conductor's debut concert. It has to set the tone of a whole new era. By that measure, Thomas Søndergård, the new principal conductor of the BBC National Orchestra of Wales, chose very shrewdly for his debut concert on Friday. He bounced onto the podium, a blonde, curly-haired figure who looked at least 10 years younger than his 43 years, spoke a few words of welcome, and launched straight into Expo by Finnish composer Magnus Lindberg. This is a typically gorgeous show-piece, which glances at Ravel and John Adams in its giddy onward rush. It made the orchestra sound like a million dollars, and showed just how neatly Søndergård can negotiate tricky tempo changes. It was a shock to go from that musical lava-flow to the delicate, salon understatement of four songs by Edvard Grieg. Danish soprano Inger Dam-Jensen conjured an innocent tone which made the songs seem affecting, rather than precious. The Strauss songs that followed were on an altogether bigger canvas, and Dam-Jensen seemed overwhelmed by the orchestra at times. But she performed the songs so winningly that their emotional core survived unscathed. All this was heart-warming and enjoyable, but the two big orchestral pieces at the concert's heart took longer to find their form. Perhaps it was first-night nerves that made the beginning of Strauss's portrait of the "prankster" Till Eulenspiegel seem careful and finicky. Or perhaps it was the over-precise controlling hand Søndergård brought to it. Fortunately the performance thawed as it progressed. Something similar happened in Sibelius's Fifth Symphony, which began uncertainly, but eventually turned into something really remarkable. It's a popular piece, but also astonishingly radical in the way different speeds rise to the music's surface and then sink down again (just as they did in Lindberg's piece, a connection which was surely intended). The middle movement can seem like a charming interlude amidst all the storm and stress, but Sondegard's very deliberate pace and careful building of tension brought out the music's vein of steel However, in this piece everything hinges on the closing bars, where the tension can become well-nigh unbearable (and was so in this performance). The final six hammer-blows have to hit home with a sense of iron necessity, and Søndergård's and the orchestra's aim never faltered. It was a tremendous ending to the concert, and a hopeful portent of things to come.