Orchestra of the Age of Enlightenment/Sir Roger Norrington, Royal Festival Hall, London

Is it a real, liturgical Mass or an ideal, meta-Mass? Is it a unified "work" at all or an ultimate compilation? All that is known for sure about JS Bach's vast Mass in B Minor, assembled in his final decade, is that its constituents ranged from sections, such as the "Sanctus", composed and performed decades earlier, to a strangely chromatic moment of vision near the end of the "Credo" that may well be the last thing he worked on. Whether or not he ever envisaged a complete performance, it is virtually certain he never heard one.

How it should be performed raises yet more questions. Earlier last century, it was customary to give it grandly, with massed choruses. Then, a couple of decades back, Joshua Rifkin, pushing his line that Bach's choirs used only single voices per part, recorded it with just eight singers. Sir Roger Norrington fielded a respectable 70 performers for his latest realisation: four soloists, chorus of 33 voices and 33 period players of the Orchestra of the Age of Enlightenment. But, given his penchant for lightly tripping tempi, the results at times had a mundane modesty. This was particularly true of some of the arias. One certainly sensed that the silvery soprano soloist Rosemary Joshua would have liked more room to phrase in her "Laudamus te" – or, indeed, the plangent mezzo Susan Bickley in her "Agnus Dei" – than Norrington's momentum allowed. For that matter, the opening chords of the first choral fugue of the "Kyrie", traditionally given an invocatory weight, were brushed aside with almost shocking casualness. But with the jubilant opening chorus of the "Gloria" the performance began to swing. Conducting without score, Norrington embarked on the first of his ecstatic walkabouts at "Et in terra pax"; by the "Osanna" he was cutting comic capers.

Some genuine insights were imparted. The "Crucifixus", usually the work's heart of sorrow, was launched with a cruel crunch that only made its final ebbing away the more telling. The tenor soloist Mark Padmore was allowed more leeway to elegantly phrase the "Benedictus". And as the seraphic trumpets climbed serenely to the heights in the culminating "Dona Nobis Pacem", it was possible to feel the entire score had been gripped together in a single sweep. A capacity audience including Sir Simon Rattle, no less, certainly seemed to think so.