St John Passion, Sheldonian Theatre, Oxford, St John's, Smith Square, London, ****

The Easter season offers the chance to compare different renditions of Bach's Passion settings – especially the shorter St John version. Gone are the old days of soupy performances in English with audience participation; authenticity is now indispensible. But authenticity still comes in degrees – which is what made the performance by New College Choir, in Oxford's Sheldonian Theatre, so very intriguing.

Edward Higginbottom, the director, fairly claims that this version was about as close as possible to the circumstances of Bach's own day – an all-male Protestant church choir linked to a university; a period instrumental ensemble, Collegium Novum, and all the soloists former New College singers. The results – effectively a live version of their new Naxos recording – were impressive. Higginbottom adopted a sort of "theatre in the round" approach – soloists addressing one another across the circle and turning to the audience at dramatic moments. From the surging opening chorus, the rich New College sound was unmistakable, well phrased and balanced, though with an occasional sense of strain in the trebles, later on. The drama was held together by a tremendously vivid Evangelist, James Gilchrist, who also ended up singing the tenor arias, too; John Bernays made a dignified Christus, while James Bowman showed a quiet mastery in his two arias – specially the heart-breaking "It is finished". Last, but not least, the treble soloist Joseph Littlewood was remarkably confident and sophisticated, without losing that essential quality of innocence. If the new recording is half as good as this performance, it should prove a classic.

St John's, Smith Square, saw Stephen Layton and Polyphony offer their London version of the piece, on Good Friday. Layton brought out the intense emotion and drama from the start – the sublime opening chorus was shattering – and he pushed the story on almost breathlessly. The occasional tempo verged on the manic, but the effect was gripping. A fresh face on the British scene, the Swedish tenor Anders Dahlin's voice was beautifully clear and expressive, but he perhaps lacked the degree of presence that the Evangelist demands; Stephen Roberts made a powerful, if grandiose Christus. Gillian Keith's pure tone was a delight, though in retrospective comparison with a boy treble, it was of course a much bigger and more "knowing" sound – two different approaches, each valid in their own way.

Once again, James Bowman provided the high point of the solo singing in his moving "Es ist vollbracht". The Academy of Ancient Instruments provided most expressive obbligato playing, but the outstanding feature was the superbly unified, balanced and expressive choral singing of Polyphony – a real wonder. Which proves that, in the end, whatever degree of authenticity you go for, it's the sheer musicality that matters in a work such as this.