The main musical themes are introduced by woodwinds, with delicate but harmonically advanced accompaniment of muted horns, strings and harp. Recurring tools in Debussy's compositional arsenal make appearances in this piece: extended whole-tone scale runs, harmonic fluidity without lengthy modulations between central keys, and tritones in both melody and harmony. The opening flute solo consists of a chromatic descent to a tritone below the original pitch and then subsequent ascent. The development of the slow main theme transitions smoothly between , , and . Debussy uses sophisticated voicings and orchestration, allowing the main melodic cell to move from solo flute to oboe, back to solo flute, then to two unison flutes (yielding a completely different atmosphere to the melody), then to clarinet, and so on. Even the accompaniment explores alternate voicings: the flute duo's crescendo during their melodic cells accompany "legato" strings with violas carrying the soprano part over alto violins (the tone of a viola in its upper register being especially pronounced).