Donald Runnicles is widely tipped as a contender for chief conductor of the BBC Symphony Orchestra when Leonard Slatkin leaves next year. Whether the Scottish-born, American-based maestro fits the bill is another question. His reputation has been made in the operatic repertory, and his ongoing BBCSO series, which places each act of Tristan und Isolde alongside a work inspired by Wagner's score, shows his strengths and weaknesses.

In this instance, act two of Wagner's masterpiece comes with Strauss's Metamorphosen. Both works are unthinkable without Beethoven's Eroica: the horn calls, with which Wagner portrays the hunt that runs his adulterous lovers to ground, derive from the symphony's Trio, and Strauss quotes the Eroica's funeral march in the final bars of Metamorphosen. Strauss also quotes act two of Tristan. Metamorphosen, written as the second world war drew to a close, is a howl of lamentation for the fatal betrayal of German culture by the Nazi regime, with which Strauss had briefly been complicit and under which he later suffered.

Here, it is Wagner who grabs Runnicles's attention. His judgment of the ebb and flow of the score's immense span is perfect. The great love duet is both erotic and mystical, although, unlike many interpreters, Runnicles does not release the tension after King Marke's arrival. The singing is tremendous, too. Christine Brewer, as Isolde, unleashes a torrent of sound throughout, and John Treleaven's Tristan is sung with finesse. Peter Rose is the melancholy Marke. Only Dagmar Peckova, unsteady as Brangäne, disappoints.

In Metamorphosen, however, Runnicles's approach is dispassionate. The playing, so eloquent in Tristan, is scrupulous rather than committed, and what should be harrowing is frequently chilly. That Runnicles can be a great Strauss conductor is beyond dispute, as proved by his Berlin performances of Der Rosenkavalier a few years ago. Rosenkavalier is, of course, an opera, and it is perhaps in Britain's opera houses that we need to hear Runnicles conduct.