Bach's first biographer, Johann Forkel, dubbed BWV910 - 916 ‘Jugendübungen’, but the toccatas are decidedly more than 'youthful exercises. In them the emerging composer cut his teeth in the flamboyant, improvisatory ‘phantasticus' style, and delved into improbably extended fugal writing (the C minor’s spreading luxuriantly across ten pages in the Bärenreiter Urtext). They overflow with the passions and excesses of youth, and, consumed end-to-end, can make for a daunting listen. But under Mahan Esfahani’s fleet fingers, and even fleeter imagination, they positively fly—invigorating vehicles for his custom-built harpsichord complete with thunderous 16-foot stop whose bottom Ds in BWV913 sound like heralds of the apocalypse.

If his fondness for the 16-foot beast can occasionally become a little wearying, and the instrument’s hearty resonance in a closely recorded sound picture sometimes obtrudes, these are readily forgotten as Esfahani continually finds more in the music than the page might suggest. (There’s a section in the F sharp minor where Bach surrenders to a sequence that goes round and round like a piece of forlorn luggage abandoned on an airport carousel!) Fugues that in other performances outstay their welcome simply don’t. Esfahani perfectly understands the toccatas’ architecture, yet celebrates their quirkiness and, interrogating every note, is generous with expressive pauses. Perhaps the D major’s first Allegro is a tad brusque, but the über-phantasticus opening to the D minor is relished to its Gothic hilt; the pacing of the epic C minor fugue is masterly; and its G minor cousin’s all-consuming swagger is irresistible.