HHHHH

APART from the largely-stunning playing and singing in the BBC SSO's amazing concert on Thursday night, with the short first half given over to Richard Strauss's Metamorphosen for 23 solo strings, and the longer second half filled with a passionate, heartbreaking performance of Act 3 of Wagner's Tristan and Isolde, completing the orchestra's three-stage performance of Wagner's epochal opera, one thing defined the night for this listener.

On our wee patch in Scotland, with three major orchestras and their array of music directors, principal conductors, principal guest conductors, associate conductors and all the other conductors who comprise the house teams, I know none who understand better the principle and practice of momentum in music than Donald Runnicles. It characterised and propelled the SSO's performance of Metamorphosen, which was never a funeral march and never a dirge, but a restless, seething canvas of counterpoint, whose complex textures moved ever-forward, illuminated by Runnicles's mastery of momentum in the piece. Momentum is not speed. It is the organic flow of the music that propels it from point to point and start to end. A conductor can either do it or he can't.

And exactly the same principle emerged from Runnicles's shattering pacing of Tristan, where momentum was constantly in flux. It's like breathing: different states, different rates; none of them arithmetical. Then, with the desperate passion of Robert Dean Smith's mortally-wounded Tristan and Petra Maria Schnitzer's rather fatalistic Isolde woven into this brew, Markus Eiche's blow-away Kurwenal, the inimitable Matthew Best, in just a few lines a towering King Mark, and Jane Irwin's Brangane fidelity incarnate, Runnicles and his troops stormed the heavens. What a night.