Elisabeth Leonskaja had a productive lockdown. For her first release since returning to Warner Classics she has recorded the complete Mozart sonatas. Previously the nearest she got to this repertoire were her 1995 recordings with Sviatoslav Richter playing Grieg’s arrangements of Mozart. You can see why they were were drawn to one another (Richter became something of a mentor for her), for they are woven from the same cloth artistically speaking and this set is full of strong, confident, gauntlet-throwing-down playing. She has been brightly captured by the Warner engineers, close enough to hear her breathing on occasion.

But let’s cut to the chase: when she recorded these last year she was already 75 and there’s nowhere to hide in these sonatas. Even more remarkably, it seems it took a mere six days in January and March to complete them – that’s an incredible one disc a day, which would daunt many artists half her age.

From the very earliest sonatas, K279 283, there’s plenty of energy on display, with a propensity for lively tempos in the outer movements and a palpable enjoyment of accentuation and forte-piano contrasts. To the opening Allegro assai of K280, for instance, she brings a bold brilliance, and finds a pleasing legato contrast at the move into triplets.

Everywhere there’s a sense that she is utterly at home with the structure of these pieces and is a clear-sighted guide. But sometimes details seem gesturally a little oversized for this music: the finale of K279, for instance, is a touch too fiercely Beethovenian. Filigree can sometimes suffer at her tempos as well, lending the performances a certain instability, though some may find this less of an issue than I do. K281’s opening movement is a real test, with the different elements – trills, triplets, martial phrases – all needing to be perfectly balanced. Leonskaja sounds a bit studied, certainly compared to Lars Vogt, who has an enviable naturalness that follows through into an undulating Andante amoroso. And Leonskaja’s finale, a real opera buffa opportunity, is short on joy and playfulness, compared to Vogt and Uchida.

Space precludes a detailed analysis of each sonata, so let me focus on a few as examples of her approach as a whole. The songful simplicity of the opening theme of the G major, K283, is much harder than it sounds and I find Leonskaja too knowing here. Turn to Zacharias and immediately there’s a directness of utterance and the subtlest of phrasing. He’s wonderful in the brilliant, Weberesque finale, too: while I can’t but admire Leonskaja’s ambition tempo-wise, some of the details are lost in the fray.

The famous K331 with its Alla turca finale is another good point of comparison. The theme itself feels a bit earnest but as Leonskaja sets off on the variations, she demonstrates a beguiling command of structure that is very appealing. She etches the Minuet and Trio into the memory and the closing Rondo is unquestionably purposeful, but I did find the octave ‘Turkish’ interjections a tad too forceful. That’s an adjective that also cropped up elsewhere in my listening notes, not least the C minor Sonata, K457, to which she adds the C minor Fantasy, K475, as a prelude. There’s a glinting steeliness from the outset of the fantasy, and I do find it’s that quality that remains in the memory, with the consoling melody in D major (for instance) passing for relatively little. Beethoven is the muse in the sonata, and of course that is an entirely valid approach, but I find that her reluctance to soften, literally and metaphorically, makes this a one-sided interpretation. Compare Brendel in 2000, where there’s toughness aplenty (and a real urgency) but it’s balanced by gentler passages that are beautifully pedalled, while in the finale she doesn’t quite match Brendel’s one-in-a-bar chase.

With the final sonata, K576, we set the seal on what is – let’s not forget – a remarkable project, if to my ears a flawed one. Again, Leonskaja brings to the outer movements boldness and spirit, but in the hunting-infused first I was worried the rider was about to get entangled in the overhanging branches. Zacharias, on the other hand, irresistibly combines bounding energy and a sureness of technique.

Even if Leonskaja isn’t the most natural of Mozartians, there’s no question that we’re in the presence of a pianist of true stature, and it will be interesting to hear what she does next with Warner.