Being a composer from the Austro-Germanic tradition (Mozart-Haydn-Beethoven and, above all, Wagner), Strauss was a composer who worked from small ‘cells’ or motives to derive a cyclical, through-composed texture for his scores. The influence of Wagner was so strong that Strauss was unable to break with the leitmotif practice, attaching certain motives (or brief, musical ideas) to characters, situations and psychological characteristics. Unlike Wagner he was much freer with his use of the leitmotif and not tied to any kind of dogmatic consistency. The use of motives that he then develops after they appear in the score (parallel to the development of the drama) is definitely Strauss’s starting point and in the complicated comic situations of Der Rosenkavalier the motivic play almost provides a ‘road map’ to the actions of the characters.
The very opening of the opera (a three or four minute introduction that describes quite frankly the intense lovemaking of the Marschallin and her handsome young lover Octavian) introduces the first two motives of the opera. The bold, virile and sexually-charged horn theme is a motive that is attached to Octavian; the string response that immediately follows is associated with the Marschallin. Thereafter in the score these ideas are used to develop further motives to be attached to these characters. The same technique is applied to the other characters Ochs, Sophie, Faninal, etc.
The use of the Viennese waltz form throughout the opera, although anachronistic (no such form of the waltz existed in 1740s Vienna), gives the right sense of ‘lightness’ and atmosphere to the score. Italian audiences were shocked by the inclusion of the waltz, the Viennese (critics, at least) dismissed it, but most audiences are charmed by the various appearances of the dance form. It’s been pointed out by Georg Solti that the waltz is a musical metaphor in the opera for characters lying, hiding their identities or practicing some sort of subterfuge. This description bears up extremely well throughout especially given the character of some of these waltz statements: something rustic (a ländler, perhaps?) for Octavian’s Mariandel, something awkward and bumptious for Ochs, something more elegant and operetta-like for the Marschallin. Think of Der Rosenkavalier as a multi-layered and more brilliantly orchestrated Die Fledermaus and one has a good basis for beginning to understand its music!