I did this pretty quickly, and I know that some of the rhythms are wrong and the pitches may be incorrect in the obvious trouble zones, but the essence of it is pretty faithful.
I marked a few areas for explanation.
1. There's a basso ostinato, a repeating bassline. This one is two measures long and sticks within the lower tetrachord of E minor (E F# G A), so it firmly puts us in E minor without giving so much that we can't go anywhere else.
2. The tubular bells strike a Bb, which is not in the key. This particular note is a tritone away from the tonic (which is constantly reiterated by the ground bass), so it sounds outside. The timbre of the tubular bells is also very exotic, which helps that note sound spooky and even more outside.
3. This is the first of those flourishes. It sounds really out there, but it's quite logical. First, it starts on a common melodic figure: the movement of the dominant (B) to the tonic (E). The rest of its effect comes from bimodality: the bass is doing that E minor thing, and if you look at the flute (or whatever that is), it's doing E major. (Remember that Eb is enharmonically equivalent to D# here.) This figure cadences on D, the seventh scale degree of E natural minor, and not a particularly stable harmonic function. The rhythm I have on this figure is wrong, but whatever.
4. Most of the melody is diatonic. Notice that the note on the downbeat is ornamented with a grace note. Also, the last note of these figures is unresolved. Up through measure 6 (the normal-sounding bit), the melody rests on F#, a member of the dominant triad. It seems that the melodies end on dissonant notes, but begin on (or center around) consonant ones.
5. Latin rhythms. The syncopations give a sense of jazzy night music. In measure 4 (and in measure 6), there's a blue note (Bb).
6. I spent less time in this one than I did in the first one. I hear sequences of diminished triads. The first one (E°) emphasizes that b5 we've been hearing since the beginning in the bells. The last three notes of this measure, and the downbeat of the next measure, form an A#°7 chord (A# C# E G), which is enharmonically equivalent to an E°7 chord (E G Bb Db).
7. A# (Bb) diminished triad in the synth.
To sum up this passage, these are my findings:
• The melody is about notes on the downbeat being preceded by elaborate anacruses. The anacruses are either diatonic and bluesy/jazzy, or highly chromatic and covering a wide range. The first chromatic anacrusis (1) is built by placing the major mode against the minor mode, and the second (6) arises from planed diminished harmonies.
• From a harmonic standpoint, E minor is the undisputed key. Bb, while present in nearly every bar, is not a regular member of the scale, and should be regarded as a chromatic tone. The tritonal juxtaposition of E and Bb is responsible for the dark and mysterious atmosphere of the passage.
• Basically, if you want to make music like this, have a ground bass in a minor key and dick around with putting b5's in every now and then, see what sort of fun you can have with bimodality and bitonality, and throw in some polychordal ideas like E°7/Em.