That heart-stopping kind of expression—not just in music but in animation and manga too—comes, I think, from contrast, from gaps. On that front, Made in Abyss is a work with an almost glaringly obvious gap between its art style, its story, and its grotesque imagery. To borrow a slightly older example: in Puella Magi Madoka Magica, the art style felt perfectly at home with the story up through episode 2, but the gap with the story from episode 3 onward was so jarring that the real-time online reaction was something to behold. Made in Abyss has an even more violent gap than Madoka (and because the heartwarming stretches run long, it feels even more violent still), and it gained a core following that spread by word of mouth online, with praise outweighing criticism in a love-it-or-hate-it way. I'm one of those people who got into it after seeing that online buzz and thinking, “If it's that amazing, maybe I'll give it a watch.” Maybe people are just helplessly drawn to things with violent contrasts.
Well, even with advance warning, the moment I actually watched it I went, “Yikes…”
Beyond Expression as Music
And I'd say Made in Abyss's score plays a role in that gap, too.
Something so terrifying it freezes your spine, lurking within scenery that looks beautiful at a glance; the emotion—somewhere between courage and fear—that wells up when the young protagonist, looking exactly as childlike as she is, must gradually face a cruel reality; the abyss within an epic scale. These pieces stir the viewer's emotions during the many scenes where you don't even know how to put what you feel into words, and they fully express the characters' inner states and a worldview deep beyond measure. There are many pieces with a mystical resonance, but on the whole, in terms of pitch there's the contrast of deep lows and high highs, plus contrasts in volume and sound pressure, very beautiful melodic structures with just a touch of dissonance mixed in, melodies that press in on you with fast, anxious rhythms that goad you forward, sudden rests, and so on. In other words, they unfold with bold, daring techniques—musically abrupt, even contradictory—that you'd normally avoid when composing an ordinary pop song. That's precisely why Made in Abyss's score is so brimming with a strange charm: it pulls you in across the board, throws your emotions into turmoil as you listen, and yet makes you want to keep listening forever. I think that contradictory feeling of “scary yet beautiful” comes from techniques like these.
The original manga is extremely interesting in its own right, but there's no doubt that the reason the anime feels even more captivating owes a great deal to the power of this work's score.
And Above All, the Overwhelming “Hanezeve Caradhina”
When you say “score,” people usually picture something instrumental, and many might feel that if there are vocals, surely it's an insert song. But this piece is said to be built on a “language that doesn't exist on Earth,” so I get the sense the voice is used as just another instrument, and I've chosen to think of it as a kind of score. (As an aside, Hiroshi Saito, who sings this song, is a fellow musician from my hometown of Sapporo, and just recently we even performed at the same show in Shibuya. I really hope you'll hear that overwhelming voice live at least once.)
Within this single piece alone, all sorts of emotions well up—homesickness, the courage of that first step into the unknown, an interest that's frightening yet alluring. And a melody so hopelessly beautiful it reaches straight into your heart. Even I, who've listened to all kinds of music, have heard a piece that fits the anime and the original's concept this perfectly only a handful of times—I could count them on one hand.
Some people talk about Made in Abyss as if it were fortunate to have spread so widely through online word of mouth, but it's no exaggeration to say its success was made rock-solid precisely because it had a score that resonates in the heart. Please enjoy it together with the anime.

From the official Made in Abyss site