Bernard Haitink's is an enigmatic art. The 88-year-old's conducting style is modest and self-contained, yet he is also capable of drawing performances of great emotional depth. Haitink closed La Scala's symphonic season with Beethoven's Missa solemnis in what was only his second performance at the house after his debut last year. This was as complete an expression of Beethoven's homage to the human spirit as one could hope for, but it left one lingering question unresolved: what is it that Haitink does in rehearsals to draw such improbably inspired performances?

Bernard Haitink © Teatro alla Scala
Bernard Haitink
© Teatro alla Scala

While Beethoven was not overtly religious, his Missa solemnis attests to his deep spirituality. It is an appropriately monumental work, not only for the demands the composer's second longest piece after Fidelio places on its performers, but also for the depth of sentiment it expresses. Haitink's approach adds little in the way of apparent individuality, nor does it seek to drive the drama as other celebrated interpretations have done. Rather, the conductor favours measured tempi and unfussy direction, allowing the work to stand mountain-like as an expression of its own intrinsic magnificence.

Much of the credit for the considerable impact of this performance must go to the chorus. This is no buttoned-up ensemble overly concerned with blend or clean phrasing, but rather an unshackled, powerful unit capable of creating a wall of sound even in La Scala's challenging acoustic. Each of these individual sections is robust, though none more clearly than the tenors, who are rare amongst choruses for producing the unmistakably focussed and pulpy sound of collective turned voices above the passaggio. Taken together, amassed vocal resources are seemingly exhaustible. The Kyrie rolled inexorably forwards like a lava flow, and the 20-minute-long Gloria remained white hot right from the tenors' opening clarion call. There was also judicious pacing under Haitink's watch – pressure built steadily throughout the Gloria, before the air instantly cleared when the fugal In gloria patris was sent crackling through the auditorium.

Not that this was in any way a two-dimensional performance. Singers and players were highly responsive to Haitink's gestures, allowing Beethoven's quickly-shifting textures to be vividly conveyed. While the Te Deum was appropriately rousingbass roars of Credo built to a statuesque Consubstantialem and a quick-fire Et ascendit in caelum – this tract was also punctuated with moments of introspection, for example with a glowing choral passage for Et incarnatus est underpinned by shadowy playing from the orchestra. The Sanctus unfurled beautifully and gave way to sulphuric runs in the Pleni sunt coeli. Shortly after, the lead violinist's birdsong solo above the choir's hushed Benedictus was especially moving for its purity of sound, as were the tenors' Hosannas that soar heavenwards at the end of the movement.

Soloists' contributions were not so consistently strong – at times, singing was mal-coordinated, and baritone Hanno Müller-Brachmann's solo contribution in the Agnus Dei was one of a few ropey individual moments. But mezzo Gerhild Romberger communicated real drama in her burnished voice whenever she sang, and while soprano Camilla Tilling sometimes squawked her top notes she spun an expressive, lustrous tone for the most part. The Agnus Dei is perhaps the spiritual core of this piece. The moment that the clouds parted on gloomy playing on the chorus's Donna nobis pacem neatly summed up what was a highly uplifting performance.