As with every German opera written after Richard Wagner, the leitmotif is an important technique used in Richard Strauss's Salome. His edition of Berlioz' Traité d'instrumentation was being prepared while he was writing the opera, so it stands to reason that brilliance of orchestration and focus on leitmotifs were things that were of utmost importance for him at the time: "Richard Wagner's scores are the alpha and omega of my additions to this work," he said of the treatise. "They embody the only important progress in the art of instrumentation since Berlioz."
One could consider Salome as a kind of "tone poem" for the stage, and if you are familiar with Strauss's Til Eulenspiegel, Don Juan, Also Sprach Zarathustra or Don Quixote you will understand that pictorial representation was crucial in the composer's attempt to communicate atmosphere, story and character. In order to achieve the necessary effects, he calls for an orchestra of 105 players! This often necessitates an approved orchestral reduction as very few orchestra pits in the world can handle that many players. The easiest pictorial effects to hear in Salome are those that quite specifically attach themselves to an image in the text. For instance when Salome refers to John the Baptist's (Jokanaan) hair, comparing it to the cedars of Lebanon which give refuge to lions, the brass instruments roar. When she threatens to throw Jokanaan's head to the watchdogs, the muted horn section 'barks' appropriately. In one of his scenes Herod reacts to the cold and an icy wind that he seems to feel: the orchestral 'comment' is extremely naturalistic and has a 'cold' aspect, but as well bears reference to the psychological and emotional state of the character. This is all part of the craft of Strauss, something that he developed a talent for in those brilliant tone poems.
Similarly, we have the leitmotifs, one for each character or group of characters (the Jews) in the opera. But his sense of development was looser than Wagner's, so often it is not possible (certainly not on first hearing) to track these musical ideas. Generally speaking, however, the music of Jokanaan is diatonic and declamatory, as if everything the character speaks is the 'word of God'. Salome's music is often dance-like and light, but with angular twists and turns. The music of Herod and Herodias can be described as purposely ugly and abrasive, with barnacled effects in the brass and winds. The fabric of the work is complex but there are tunes which recur and capture the attention of the ear. Familiarity with the work reveals more and more levels of beauty, but its surface beauty is certainly the brilliance of the orchestration which is endlessly fascinating.