If I had to choose between Dennou Coil’s OP or ED, Prism and Sora no Kakera respectively, I’d opt for the latter as more representative of the series as a whole. Prism has a synthesizer element that is made more apparent (and prominent) in its full length version.
Unlike other series or movies where the technology is always in your face, I only occasionally felt that way with Dennou Coil. From the perspective of the kids, there is no difference between the real world and the enhanced one enabled by their glasses, even though one of the many “improvements” is the Searchmaton. It’s that sense of seamless of integration that makes the technology nearly indistinguishable from magic.
Likewise, the OST has an organic feel. Synthesizers are used sparingly and instead the nod is given to orchestra, piano, guitar, and woodwinds. Brass also seems to be in short supply, and this soundtrack is generally subdued and understated as a result.
Some of my favourite pieces are where Saito Tsuneyoshi creates haunting or hazy soundscapes, many of them associated with scenes about or inside the Coil Domain. Their titles are listed below in order of appearance. In all cases, I never cease to be wrapped in the covered tones of the instrumentation.
(Light spoilers ahoy!)
CD 1
04. Kanashimi no Kako is not one of those favourite pieces, but it’s solo piano, Romantic era influenced, and it’s got a strong 3/4 time, so it automatically deserves mention. Bright, cascading solid chords in the right hand just seals the deal. It sounds a lot like chord practice. The memories.
I don’t remember where 06. Isekai appears, if it ever does. It’s also not a favourite piece. I’m off to a great start here. It’s different, and a good example of the other “different” pieces that can be found on the OST. They also deviate from conventional composition but this is one of the more extreme cases.
A woodwind chamber group is used, and the first thing you’d notice about the music is its use of medieval modes instead of the more widespread concept of tonality. There is also a distinct lack of harmony and harmonic progression as we know it, as was also the case in pre-Renaissance music. The support instruments only play the root and the fifth above it, resulting in a hollow sound because of the absent defining third.
09. Kanashimi is used to great effect in the second half, its totality reserved for the darkest of situations. The opening lines are segmented and used to cue the viewer on the shadowy elements of the virtual world. But just past that is a mournful motif on top of which is built a violin line desperate in its pace, panicked shrillness at its height and despair at its bottom. Behind it all, guitar and hand drums are driving to a conclusion that is anything but certain.
12. Machi no Tomoshibi appears briefly as Haraken is taken back to his body in episode 20, but its defining moment is the lyrical interplay between flute and cello. That entire section, the B part in its ternary form, is marked by fluid melody passing between flute, oboe, and strings. One of the warmest pieces on the OST, yet bittersweet.
14. Shizuka na Yoru 2 has, as one might guess, two versions. The first one is faster in tempo and played by an entire string section, while this one is for a woodwind chamber group. One amusing note is that one can hear keys being pressed on the bassoon (I think). The woodwind version brings more haze out of this Baroque styled piece. It’s not a fugue, but there’s some counterpoint work and the individual lines are balanced.
18. Yuuyake has the typical slice of life rhythmic acoustic guitar, but it is at points more relaxing and more dignified, determined by whether the solo harmonica, solo recorder, or violins carry the melodic line. Not one of my favourite tracks, but its appeal grows over time. Maybe just a little too short, but short pieces are an unfortunate reality in OST’s.
One of the most fully scored moments occurs, appropriately, amid the maelstrom of a collapsing 4-4-2-3 and Coil Domain, and it belongs to 19. Yuujou. The theme with which it’s built is tempered and graceful, and as the piece unfolds from solo piano to piano plus orchestra, we see that friendship is more warm and dignified than heroic and triumphant.
CD 2
I think 01. Sora no Kakera TV EDIT got better once I finished the series. The terminal point of Densuke’s path in the ED sequence and the lyrics just knocked me down when everything came together. It’s got that same uplifting but dignified feel that permeates the other tracks, a song about (for?) Yasako from Isako’s perspective.
The TV version places the last phrase closer to the second last. Doing so produces a stronger finish.
03. Tomadoi is pretty adventurous, but it doesn’t start out that way. Moments of stillness in the opening guitar line develop into a diffuse, late afternoon haze with the addition of the string section. A beacon steps forward with the introduction of the flute, and then the oboe, and then the uncertainty is literally swept away in a flash of clarity.
Its use during scenes with revelations is apt. I’d have this piece accompany all my epiphanies if possible, but I wouldn’t notice a difference whether it was or not.
06. Komorebi is the primary cue for urban legends and other information associated with the Coil Domain. Another woodwind chamber piece, it starts out sans harmony and slightly modal in its opening phrase, and ends on octaves and fifths, emphasizing the point that the Coil Domain is decidedly foreign territory. Elsewhere, it is carried by a wavering undercurrent that moves around the lower ranged instruments. Its harmony feels a bit more chromatic than Shizuka na Yoru but it may just be me hearing things that aren’t there.
13. Hyouryuu is like a clock. You can hear the clock’s pulse in the crystal clear piano line, see the quiver of the stopped second hand in the piano’s ringing. There’s a sense of polish in the clean minimalism of the piece and the whirring of gears as the strings come in. The oboe line gives the perpetual motion machine just enough direction so that you don’t become hypnotized. It always ends too early.
14. Kodoku is a lonelier version of the opening theme in Machi no Tomoshibi, as maybe it should be given its title. Prominent English horn (or bassoon?) with harp and strings for accompaniment. At the end, the harp has its own section where it sprinkles its notes, producing the scattering effect for when Kanna fades away, and when Yasako says her final goodbye to Densuke.

2 Comments
If you’re going to talk about the anime soundtrack, just some trivia – try listening to some of Tsuneyoshi Saito’s other works. I’ve found out that Yuujou from Dennou Coil CD1 is almost exactly the same as Mirai-Kako from the Fafner soudntrack. And I’m absolutely positive that a track almost exactly like the first half of Shinmi from CD1 can be found on the Kaze no Yojimbo soundtrack.
One day I want to collect all of Saito’s soundtracks and see which tracks he’s reused.
I’m not familiar with the appreciation of music, but personally my favourite from this soundtrack is Kanashimi, I guess. And then maybe Egao (it brings a smile to my face too). In a way, I do like even the awkward sounding ones like Fushigi na Koe (Satchiiiii!), Warudakumi and Tatakai simply because of the memories of watching this show. I agree with you that I love the way Tomadoi is used for revelations.
You’re absolutely right about Yuujou. It’s bit thinner than Mirai-Kako in the busy parts, but it’s also noticeably clearer as a result.
Unfortunately my exposure to OST’s in general is limited to series I watch, and it’s a relatively short list at the moment.