Adagio in B minor K.540 (1788)

The Adagio in B minor, one of the most intriguing of all Mozart’s piano works, is the subject of endless speculation. All we can be sure about is that the composer entered it in the catalogue of his works on 19 March 1788 – which is useful information but no explanation of the anguish so clearly expressed in all but the last few bars. Could it be a symptom of the depression he is said to have experienced, in severely straitened financial circumstances, in the late 1780s? Could it be a delayed reaction to the death of his father ten months earlier?    Or could it be could the result of a purely professional decision to investigate the possibilities of B minor, a key he had used in an instrumental work only once before?

Whatever motivated its composition, its expression is intense and detailed with a (for the period) rare precision in phrasing and dynamic markings. The harmonies sustain an unfailing tension by means not so much of the predominantly minor modality as of frequent suspensions and diminished sevenths. The first diminished seventh is the first chord in the first bar where it is emphasised by a sforzando in a piano context. Similar contrasts persist throughout. The second entry of the main theme is consigned to the left hand, adding a dark colouring which is further exploited in an episode of hand-crossing through three upward octaves. The most dramatic examples of hand-crossing are those in the development where the right not only exchanges phrases between treble and bass but also aggravates the bass response by repeating it a tone lower.

Not the least extraordinary feature of the work is that after a regular sonata-form construction – with a second subject introduced in F sharp minor minor and recapitulated in B minor – a seven-bar coda ends it in a serene B major.   

It is as though he had just discovered B minor for the first time. Of course, there are passages in B minor in Mozart’s music at all stages of his career but remarkably few movements in larger works are actually set in that key and only this one independent piece. There has been speculation, inevitably, about what could have happened to Mozart in March 1788 to inspire such tortured harmonic expression as that of the Adagio in B minor. But there is no reason why a composer in a perfectly balanced state of mind shouldn’t set out to investigate a tonality he has hitherto avoided or, for whatever reason, neglected.

What interests Mozart here is not so much the melodic as the harmonic and colour potential of B minor. The whole work seems to grow from the dissonance in the very first bar where the main theme, nothing more than the three notes of the B minor triad, meets a diminished seventh. That misadventure, intensified by a sforzando, provokes the drooping chromatic sighs that, varying dramatically between f and p, follow in the right hand over repeated chords in the left. The same dynamic colouring is applied to the second subject, no more than the three notes of the D major triad, rising from low in the left hand which then crosses the repeated chords in the right to form an upward chromatic sigh.

The exposition (which is usually repeated) seems to end peacefully enough in D major. It is plunged, however, by an abrupt modulation to G major into the development, which examines this minimal thematic material in detail – though again not so much for its melodic interest as to lead it into such extreme harmonic situations that it loses its sense of direction. In these circumstances the return of the diminished seventh at the beginning of the recapitulation, though still painful, is a welcome landmark. But this time there is no change to the major for the second subject, which is recalled in B minor. That key prevails into the coda and seems to be the ultimate fate of the work until, with a blissful change of mode worthy of Schubert, it slips into B major just two and a half bars before the end.