“A little piano sonata for beginners” is how Mozart described his much-loved K. 545 of 1788, yet it’s far from easy. A graceful Allegro is followed by an exquisite aria-like Andante, then a delicately chirpy Rondo whose central section develops its theme in minor tonality. K. 284 is the last and most brilliant of Mozart’s six earliest surviving sonatas, written in his late teens and performed on tour, and the only one of the set published in his lifetime. After its brightness, K. 310 in A minor is a complete contrast. When it was written during the 1778 Paris visit on which Mozart’s mother died, it’s been suggested, albeit with no evidence, that its tragic tone specifically reflects that bereavement. Either way, even its major-keyed Andante feels sorrowfully nostalgic, makes much use of minor tonality, and has its own storm clouds.