There are eight introductory measures (Assai sostenuto) which are in close polyphonic style out of a single motive. This motive is announced by the violoncello; immediately taken up, transposed, by the first violin; given again, inverted, by the violoncello; and in this form answered by the violin. The Allegro begins upon a diminished seventh chord in which all the instruments take part, and from which the first violin breaks with a descending and ascending run of sixteenth notes, founded upon the chord. The first theme is at once announced by the first violin, a theme which, distinct and full of character in itself, really rests upon the opening motive, or upon the harmonies implied in it. A single measure of adagio prepares for another start with the same material. The violin has another run, founded upon the diminished seventh chord, rising thereby to F. Under this the violoncello takes up the first theme, which is completed by the viola; while, it will be observed, the first violin, followed by the second, give out the opening motive, inverted, in augmentation. Later a transitional theme is announced in D minor by the first violin, closely imitated by the violoncello and the second violin. The true second theme follows shortly after, in F major, a peaceful melody, sung by the second violin over an accompaniment in triplets shared by viola and violoncello.
The movement is fairly regular in structure. The development is short and is based chiefly upon the opening chromatic motive, with which indeed the 'cello begins it. The restatement begins in E minor, with the familiar diminished seventh run for the first violin. The second theme appears in C major, and is given to the 'cello. There is a long coda, which, toward the end, swells over a mysterious low trill to a brilliant climax.
The next movement is really a Scherzo in A major. The instruments have four measures in unison, each measure beginning with a half-step which cannot but suggest some relationship to the chromatic motive of the first movement. But the short phrase of the first violin, begun in the fifth measure, is the real kernel of the main body of the movement. The Trio, in E major, is of magical beauty. The first section is over a droning A, shared by both violins, at first, to which the viola and 'cello soon join themselves. The melody is decidedly in folk-song manner, and is played by the first violin in high registers, and faithfully followed by the second a tenth below, both instruments maintaining at the same time their droning A.
This melody is supplanted by a lilting dance movement. The short phrases begin always on the third beat of the measure, and their accompanying harmonies are likewise syncopated, in the manner which is frequent with Brahms. The short phrases are arranged at first in dialogue fashion between first violin and viola. Later the viola converses, as it were, with itself. Only the 'cello is limited throughout the section to accompaniment. A few measures in unison between the 'cello and viola appear twice before the end of the section, the notes of which may be intended dimly to recall the chromatic motive of the first movement. A more positive phrase in alla breve time, played by second violin, viola, and 'cello in unison, brings back an epilogue echoing the opening phrases of the Trio; after which the main body of the movement is repeated.
Beethoven entitled the next movement ‘a devout song of praise, offered by a convalescent to God, in the Lydian mode.’ It probably owes its origin to the fact that Beethoven was taken seriously ill while at work on this and the B-flat major quartet. It seems likely that before this illness he had other plans for the quartet, and that the Danza tedesca before mentioned was to find a place in it.
The movement is long in performance but relatively simple in structure. The chorale melody, simply harmonized, is preceded by a short, preludizing phrase; and its strophes are set apart from each other by short interludes in the same manner. After the chorale has been once given, there is an episode in D major (Neue Kraft fühlend) of blissful, gently animated character. The chorale is then repeated, the melody an octave higher than before, the interludes and the accompaniment complicated by syncopations. Once again the D major episode, highly elaborated. Following this, the chorale is introduced once more; but the introductory phrase is greatly lengthened and developed, and there are suggested entrances of the theme in all the instruments; nor does the complete theme make itself heard, but only the first phrase of it seems ultimately to soar aloft, in yet a higher register than before. So that this last section may be taken as a coda, or as an apotheosis.
The short march which follows calls for no comment. The final allegro is introduced by recitative passages for the first violin, gaining in passion, culminating in a dramatic run over the diminished seventh chord which bears some resemblance to the opening of the allegro of the first movement. There is a passing sigh before the last movement begins, Allegro appassionato.
Compared with the quartet in A minor, that in B-flat major is simple. It is more in the nature of a suite than in that of a sonata, though the first movement presents beneath an apparently irregular outline the basis of the classical sonata-form. At first glance the frequent changes of not only key signature but time signature as well are confusing. The key signatures are now two flats, six flats, two sharps and one sharp; and at the beginning, the middle and the end of the movement the time is now triple, now duple, now slow, now fast.
The slow measures are related to the introduction, which here as in other works of Beethoven is recalled at times in the main body of the movement. The allegro makes a false start, in which the main outlines of the first theme are suggested. From the second start, however, the movement follows a relatively normal course. The first theme is compound. On the one hand, there are rapid groups of sixteenths, which play an important part in the whole movement; on the other, a rhythmical motive, rather than a theme, first announced by the second violin, which is the motto of the piece. The second theme is first presented in G-flat major by the second violin and immediately taken up by the first. At the beginning of the development section and again in the coda use is made of the motive of the introduction.
The second movement, a Presto in B-flat minor in alla breve time, with a Trio in 6/4 time, is short and in the manner of a folk-song or dance. It has no inner relation with the first movement; but it may be said to breathe something of its spirit into the following andante (D-flat major, common time). The kernel of the melody of this movement may be found in the first measure, given by viola and 'cello; and this kernel was sown, so to speak, by the previous movement. The viola develops it in the second measure and the phrase is immediately after taken up by the first violin.