There are myriad good things to say about this album. Take the crystalline execution of the Fugue in D, BWV850: Aaron Pilsan performs with nuanced exuberance, the colloquial chatter of royalty. Or the whirling delight of the Prelude in A flat, BWV862, invigorated and sensitive in equal measure. There’s a reason beyond Pilsan’s caffeinated fingerwork why these two movements a tritone apart sparkle and thrill the ears. Pilsan builds on a tradition in which the ‘well-tempered’ adjective of Bach’s title is not taken to mean equal temperament but is rather an indication of a tuning system where the fifths are slightly narrower (such as in Werckmeister). Credit must go to piano tuner Christian Schoke, who has achieved spectacular results in this regard. Schoke’s tempering not only provides an array of different timbral colours, as you would expect, but also of various qualities of light. Some keys, G major for instance, are bright with lemon-curd tartness, while others glow like jellyfish in the deep.

Pilsan, at only 26 years old, is already a fine communicator of Bach’s rhetoric. There is a sense that he has grappled with what might else be said with this music: indeed, the booklet notes tell of a holiday where, aged 16, he spent a summer studying the score of Book 1 without a piano – what might fingers create when slipping into corporeal habit isn’t possible? Where this emerges most refreshingly is in certain trade-offs. The Prelude in C minor, BWV847, isn’t a moto perpetuo machine, a tunnel vision of drama, but is rather shaded according to the strength of harmonies. That and the gorgeous articulation of bar lines makes the growth into improvisatory spin so much more organic and convincing. Or in the Prelude in D minor, BWV851, where ominous didacticism is traded for a drugged melancholy. Pilsan’s thoughtfulness reminds us why we return again and again to this music: there is so much more to be said.

There are, however, less convincing trades. I’m not wholly taken with the articulation in the Prelude in G, BWV860: some harmonic resolutions are attacked with a strange staccato not in keeping with the implicit cantabile. The Fugue in A minor, BWV865, is perhaps the least successful of the lot: the argument lacks control and cohesion, and the sound transgresses into harsh territory. These are minor criticisms in a WTC more than worth your time: bring on Book 2.