Prom 12: CBSO/Adès, Royal Albert Hall, London

Thomas Adès' leviathan of an orchestral piece, Tevot, surfaced between the two intervals of this three-tier Prom. But in the true sense of its Hebrew title – meaning, "places of safety" – it drew into its safe haven the huge audience that Mussorgsky and Borodin had lured into the hall. Tevot is that rare thing among contemporary works – in sound, it belongs resolutely to the early 20th century; but in spirit, its immediacy is very much of the here and now.

The feel of the piece – particularly in the opening, where the surface glints (arpeggiated violins and piccolos) but the depth is full fathom five – is oceanic, almost as if Adès was reluctant to leave behind the central theme of his opera The Tempest, which premiered the year before in 2004.

Tevot is the Noah's Ark on that treacherous ocean and it floats a chorale-like motif which, once it has surfaced, becomes all-pervasive. It's the transfiguration of that motif from lamentation to radiant affirmation (a touch of Janacek here, in the stratospheric fiddles and middle-range trumpets) that is guaranteed to entice even the most innocent ear. Along the way are sonorities so fantastically imagined (and realised by the City of Birmingham Symphony Orchestra) that you don't doubt this work's future in the core repertoire.

For the rest of this Prom, though, the other message was that Adès may be a prodigiously gifted composer but he is, at best, a mediocre conductor. He didn't once look at his deft and witty soloist, Louis Lortie, in Prokofiev's Piano Concerto No 1, and the woolly and unidiomatic CBSO Chorus were frankly all over the place in the big opener – the rarely heard "Sorochintsy Fair" version of Mussorgsky's A Night on the Bare Mountain. This night was anything but young, and these demons had no appetite for devilry. Little had been done to make them sound less like a Midlands coach party on an away-day to the Home Counties, and all the score's daring non-sequiturs began to sound like accidents. Awful.

At least the grizzled vocal and physical presence of John Tomlinson lent a touch of rude colour to the excerpts from Boris Godunov. The tormented Tsar's death-defying cry – "I am still the Tsar!" – was the evening's sole concession to true Russian spirit.

BBC Proms continue to 13 September (0845 401 5040)