Task: Question Answering
Input (English): Passage: The opening melody is played by a solo bassoon in a very high register, which renders the instrument almost unidentifiable; gradually other woodwind instruments are sounded and are eventually joined by strings. The sound builds up before stopping suddenly, Hill says, "just as it is bursting ecstatically into bloom". There is then a reiteration of the opening bassoon solo, now played a semitone lower.
The first dance, "Augurs of Spring", is characterised by a repetitive stamping chord in the horns and strings, based on E♭ dominant 7 superimposed on a triad of E, G♯ and B. White suggests that this bitonal combination, which Stravinsky considered the focal point of the entire work, was devised on the piano, since the constituent chords are comfortable fits for the hands on a keyboard. The rhythm of the stamping is disturbed by Stravinsky's constant shifting of the accent, on and off the beat, before the dance ends in a collapse, as if from exhaustion. Alex Ross has summed up the pattern as follows:
According to Roger Nichols (1978, p7) “At first sight there seems no pattern in the distribution of accents to the stamping chords.  Taking the initial quaver of bar 1 as a natural accent we have for the first outburst the following groups of quavers: 9, 2, 6, 3, 4, 5, 3. However, these apparently random numbers make sense when split into two groups:
Clearly the top line is decreasing, the bottom line increasing, and by respectively decreasing and increasing amounts …Whether Stravinsky worked them out like this we shall probably never know.  But the way two different rhythmic ‘orders’ interfere with each other to produced apparent chaos is… a typically Stravinskyan notion." The "Ritual of Abduction" which follows is described by Hill as "the most terrifying of musical hunts". It concludes in a series of flute trills that usher in the "Spring Rounds", in which a slow and laborious theme gradually rises to a dissonant fortissimo, a "ghastly caricature" of the episode's main tune.
Brass and percussion predominate as the "Ritual of the Rival Tribes" begins. A tune emerges on tenor and bass tubas, leading after much repetition to the entry of the Sage's procession. The music then comes to a virtual halt, "bleached free of colour" (Hill), as the Sage blesses the earth. The "Dance of the Earth" then begins, bringing Part I to a close in a series of phrases of the utmost vigour which are abruptly terminated in what Hill describes as a "blunt, brutal amputation". 
Question: What concludes in a series of flute trills that usher in the "Spring Rounds"?
Output (English): The "Ritual of Abduction".