Among the works of Bach’s last decade, The Art of Fugue is completely open in its instrumentation: on a scale from a single keyboard to the multicoloured orchestrations of yore, this new realisation is at the purist end – just four string players with the occasional (and often inaudible) harpsichord. No case is made in the notes for this approach, yet with playing of this sophistication, the restricted sound palette works wonderfully, supporting a calm, ruminative exploration of the many fugal devices. Rachel Podger’s group manages drama too in the French-style fugue, driven by the bite of the bow on the strings. The end is achingly incomplete, as is Bach’s text.