The finest part of the work is undoubtedly the second movement, an “Adagio affetuoso ed appassionato.” It is the richest in texture and certainly the most poetic and emotional of the four. When the composer played it to Amenda he is said to have inquired what the music suggested to him. “It suggests a lover’s parting,” replied Amenda; whereupon Beethoven replied, “Well, the tomb scene from _Romeo and Juliet_ was in my mind.” And Bekker insists that this Adagio is “a most moving song of sorrow such as only Beethoven could accomplish when he turned to the grave D minor key.”
The second quartet, in G major, has been christened in some German countries the “Compliment Quartet.” It is graceful and rather courtly but it reaches none of the depths of the more moving pages of the preceding work, The Finale, however, is an instance of that “unbuttoned humor” that Beethoven was to exhibit on later occasions and of which he gave us supreme instances in the last movement of the Seventh Symphony, the Eighth Symphony, and moments in the last quartets, the “Diabelli Variations,” and several of the final piano sonatas. Opus 18, No. 3, in D, is likewise marked by a quality of gaiety, though hardly of the “unbuttoned” kind.
The fourth work of the opus 18 set, in C minor, is more or less a work distinct from its companions. “A mood of deep seriousness is common to it and the C major Quintet, opus 29,” believes Bekker, “but the Quartet is full of passionate excitement,” and he alludes to its “mournful earnestness ... and restless dissatisfaction, the very opposite of the cheerful sense of concord with the world and mankind expressed in the other five.” The Quartet in A major has been termed Mozartean by some, operatic by others. Certainly it is fluent and lilting music, of which the Minuet is in some respects the most winning portion even if the final Allegro excels it in expressiveness.
The B-flat Quartet, sixth of the series, is particularly significant for the sombre adagio beginning of its otherwise jubilant allegretto Finale. Beethoven has headed this introduction (which is recalled dramatically during the movement) “La Malinconia: Questo pezzo si deve trattare colla più gran delicatezza” (“Melancholy: this piece must be played with the greatest delicacy”). This eerie and wholly romantic movement is a true glimpse of the Beethoven into whose newer world we shall presently penetrate.