When he died last November, John Tavener had already completed a number of pieces that would have served to celebrate his 70th birthday this year. Two of them were destined for the Proms, with the 12-minute Gnosis opening this BBC Symphony Orchestra concert under the ensemble's former chief conductor, Jiří Bělohlávek.
Scored for mezzo, alto flute, strings and percussion, in many ways the still, static Gnosis covers familiar Tavener territory. The title refers to spiritual knowledge, and sets a handful of words variously representing the Christian, Hindu and Islamic traditions, evoking being, consciousness, bliss, Jesus, plus the larger phrase "there is no God but Allah". The mode is simple, the solo mezzo lines – carefully shaped here by Sarah Connolly – drawing on oriental scales, while Michael Cox's flute delicately shadowed and encircled them.
Occasionally livelier, even more aggressive material interrupts, though the real surprise comes at the end, when the easy-to-whistle main theme of the finale of Mozart's G Major Piano Concerto No 17, K453, suddenly bursts through Tavener's textures, here raising a slight ripple of laughter by its amiable incongruity.
This was a sympathetic performance, balanced at the close of the programme by a reading of Shostakovich's mighty Tenth Symphony in which the orchestra demonstrated the impressively warm tonal qualities Bělohlávek always seems to draw from them. In other respects, though, and despite the cleanness and authority of the playing, this was an interpretation that could have done with greater vehemence and a sharper sense of the grotesque.
The programme's outstanding performance came in the middle, with Isabelle Faust's intense reading of Bartók's Second Violin Concerto, vividly accompanied by Bělohlávek and the orchestra, in which the soloist's complete technical command was offset by passionate engagement conveyed through rich and endlessly varied tone. In her encore, a solo Bach Sarabande, the evening reached an even higher spiritual plane than Tavener had achieved.
• The Proms continue until 13 September. Details:bbc.co.uk/proms.
