Sonata in D major for two pianos, K.448

Duet sonatas for oneself and one’s sister to play in Salzburg are one thing. A two-piano sonata to be performed at a concert in the home of the Auernhammer family in Vienna - with Mozart’s pupil, Fräulein Auernhammer¹ taking the first part and the composer himself the second - is quite another. So, although the Sonata in D major is chronologically the next four-hand work after the Salzburg sonatas, the difference in stature should not be surprising. Mozart himself had developed considerably as a composer in the seven years between 1774 and 1781 and there is more freedom in the two-piano medium.

According to the composer, the first performance was a great success. The sonata was perfectly calculated for the circumstances, with many witty exchanges between pupil and master - who remain on equal terms throughout - much keyboard brilliance and nothing too serious in expression. The exposition of the first movement is extraordinarily rich in melodic material² and it is strange that Mozart should ignore all of it and find a new theme for contrapuntal treatment in the development. The reappearance of that theme at the end of the recapitulation seals the unity of the construction.

The Andante is similarly abundant in melody and again none of it is developed. After a short middle section the exposition is simply repeated, the distribution of the material between the two instruments slightly re-adjusted, the sonorities perhaps even more voluptuous when transposed from D to G major. The Allegro molto, on the other hand, is a full-scale sonata rondo with an E minor episode which acts as a second subject.

rl 75: the daughter Josepha took piano lessons with him, and the thought her a great bore (‘seccatrice’); although apparently extremely ugly, she was an excellent pianist and in 1786 married a civil servant named Johann Bessenig.…We played…a Sonata for four hands which I composed expressly for the occasion and which was a great success.

On remarquera que le thème principal de l’Allegro con spirito est directement issu de thème du premier mouvement de la Sonate en ré majeur Op.13, No.2 de Jean-Chrétien Bach

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The difference between a piano duet and a piano duo is, or can be, the same as the difference between piano music and chamber music. Four hands at one piano (in a piano duet) can do no more than double the number of notes or melodic lines available to two hands, enriching the texture but without changing its nature. Two pianists at two pianos (in a piano duo) can interact as two different instruments, making their exchanges a clearly observable dialogue all the more meaningful for its two-sided interest.

Mozart, who wrote several piano duets but only one duo sonata, was very aware of the difference. His Sonata in D major - first performed by the composer with his pupil Josepha Auernhammer at a concert in her home in Vienna in 1781 - is chamber music rather than piano music. It is true that sometimes, for dramatic effect, he goes for the sheer weight of sound available from the two instruments in rhythmic unison, as in the heavily emphatic opening bars. Generally, however, they are less inclined to make joint statements than to exchange ideas, as they do in the engagingly scored to-and-fro presentation of the first subject. If the introduction of the second subject amounts to little more than a solo for the second piano, the texture become more involved as soon as the first piano takes up the new theme and the two of them develop it together. The vigorous exchange of on-beat and off-beat chords over a rumbling bass line is an essentially piano-duo sound, as is the entry of a third theme on first piano to the accompaniment of running semiquavers on the second. Surprisingly, considering how much material there is already, the development is based on its own theme, a descending chromatic line which sounds as though it ought to initiate a fugue and very nearly does.

Much of the Andante, like the opening theme on the first piano accompanied by gently undulating G major harmonies on the second, could have been conceived for piano duet rather than piano duo. Exchanges do take place, however, and the entry of a second theme on one instrument against an ostinato sustained on the other is a particularly attractive example of two-sided scoring. Most interesting of all is the cadenza dialogue they share when confronted by intrusive alien harmonies shortly before the end.

The last movement is a briskly resourceful sonata rondo. Exploring a wide range of textures in the variously harmonised episodes between the recurrences of the main theme, it reserves the most robust example of piano-duo scoring for the coda following the very last appearance of that cheerful little tune.