A warning first: don’t be tempted to turn up the sound because a harsh violin will dominate. The keyboard is the prime instrument in Mozart’s scheme; and a properly adjusted volume level improves the balance by reducing some of the relentlessness in Jean-François Rivest’s tone. But the timbre of David Breitman’s fortepiano varies – spiky in the Mannheim sonatas, warmer and with a ‘carrying’ (though sometimes hollow) quality in the Auernhammer set. The characteristics of both instruments seem to be products of close miking with electronic manipulation disturbing listener concentration as well. Does it make sense to attempt conjecturally authentic interpretations under inauthentic conditions?

If the recording inhibits the presentation of these performances, it nevertheless draws attention, if somewhat obtrusively, to the artistic rapport between the musicians and what they try to reveal. For instance, the change to B flat minor at the beginning of the development in the first movement of No 19 (K302 in E flat) and the corresponding difference in mood are pretty explicit. Mozart is not treated with kid gloves either here or anywhere else; but the lack of ambience is unsympathetic to the repose implicit in, say, the Andante grazioso theme and variations of No 22 (K305 in A). It is taken at a fitting tempo but with little grace because Breitman’s playing, particularly in the first variation for piano only, appears inexpressively bitty – of a dryness that might also be exaggerating the severe approach to No 21 (K304 in E minor) which for the most part is stark and matter of fact.

These are unusual lapses given that Breitman and Rivest show so often that they are no mere readers of the text; and No 25 (K377 in F) exemplifies the finest attributes of these interpretations. In the D minor Andante specifically, these artists expertly translate their feelings about the music as they transit from the melancholy of Variations 1-3 and emphatic power of Variation 4 to the melting tonic major transformation of Variation 5 with the keenest of responses.

Gary Cooper and Rachel Podger, justly balanced, are in their own way as receptive to the content of three of these sonatas. And the engineering doesn’t restrict the expansiveness of the violin or etch the notes of the keyboard. Instead, it reflects a consistent, believable acoustic for the performances to speak their messages without unwelcome distractions.