Hmmm, contemporary Touhou music discussions and analysis are ones that don't typically pop up, and as someone who is a bit opinionated and quite in favor of Touhou 17 especially, I wanna get in too. I've always been reserved when it comes to making musical analysis due to limitations pertaining to the relevant linguo plus lack of ability to distinguish the exact time signatures, but here goes :
First of all, regarding ZUN's game music, they're generally made in a way where they match specific parts of the stage (start of the stage, midboss, end of stage) AND even be arranged in a way where it capture a particular kind of mood (a rather clear objective in Touhou 17, whose motifs leans heavily into Hell and the afterlife), while in the boss themes he tries to capture certains aspects related to the boss (his reasoning for making the music such or such way can be read in his comments in the music room).
So with that in mind, here's my analysis of the stages themes for Touhou 17 first of all :
Stage 1 theme : This is Sai no Kawara. Pretty much the dead children's Limbo (heavy stuff normally), with a twist. The song opens with this weird harpsichord-like sounding instrument (not sure what the name is exactly), with strange choirs going on in the background, even bells-like instruments towards the middle : very eerie, it might as well say "haunted place". However, as we reachto the middle part of the song, Eika pops up. Choirs shut down. The squeaky instrument that played before gets more and more highkey (like I said, I'm not big on music linguo) and therefore more hopefull, less dark. This is Children's Limbo, the ghost of dead children wander about and spend their afterlife in penance, trying to pointlessly stack stones that get knocked up, yet Eika has turned the whole process into a game and a competition : the place is therefore not as sad and depresing as it should have been, but carries a bit of hope and joy, and the song reflects that before things quiet down as it prepares to loop
Stage 2 theme : The Sanzu River, basically a physical border between this world and the next. There are only the spirits who didn't reach Higan as well as creatures from more ancient era here, a friendless place where we're lost in and try to stumble or way through. The beeping instrument and the muffled ZUNpet, the repeatitiveness of it all, there's a sense of oprression as you're lost in the vast expanse of the Sanzu river ... then, boom, full stop, some semblance of normalty as we finally meet a normal(?) ish person, our potential clue towards our main goal, but then she's already gone, and we're back to the vast and uncomfortable quietude of the Sanzu River ... I like to think of the music sounding more and more clear as we reach the end of stage as symbolizing the end of our wandering about.
Stage 3 theme : Higan. Essentially the waiting room for those who are awaiting judgement for the Touhou verse. Vast expanse of red spider lillies as the eye can see, but despite this beauty, there's no life to be found. A quiet and eerie place, with nothing but ominous flowers and spirits to its name. The bells from the intro get absorbed by the main melody, where its just pleasant background noise for the muffled ZUNpet instrument, and as we reach the mid boss, where we not only get proper ZUNpets like usual, but the bells play a different tune too, a break from the monotony of Higan, before returning to business as usual. A quiet, muffled song yet with a beauty that's supported by the bells, which capture the loneliness and emptiness of Higan, yet in spite of all that, we still have the odd encounter to break the initial impression.
All in all, the first three stage from the demo are fairly eerie, capture emptiness end solitude, and the quietude provided by the muffled ZUNpet (or whatever the damn instrument's name is) as well as a generally slow pace (dunno the exact time signature but they're obviously slow and quiet sounding) are quite likely how ZUN conceives Touhou's afterlife and its empty quietude.
Stage 4 : Hell. Finally, and for real. No more melancholic nonsense, none of that corny beauty crap, it's Hell and you're gonna feel it. You're greeted by a harsh tune in the intro, a massive contrast with all the previous songs, yet there's still a bit of uncertainty with those deep pianos notes in the intro, as it builds up and up into a surprisingly relaxed melody : has the reality of it finally settled in ? We know whaat's up as the relaxed piano get absorbed into harsher ZUNtars. Yet it's not enough, we have a goal that we're searching for, more build up is necessary as we further our search, then boom, mid boss section, the first real clue towards our search, climax of the song as we dive back into the hail of bullets, there's no quiet piano anymore, only high key notes, the confidence with which we're comingfor the confrontation and the resolution of incident.
Stage 5 : Beast Metropolis. An unheard before and completely alien world, with very different value from ours. It's an actual dog eat dog, where beasts exploits beasts, and the weakest creatures of all has little choice but try to make themselves smaller in the little space given to them ... a dystopia where each and everyone is a ressource. The entire place is filled with massive skyscrapers, but beneath the pompousness of it all, the sad reality : it's not a good place to be. The slow, quiet melancholic piano tunes we get in the earlier parts of the song, captures the misery of the human spirits. But then the tempo accelerates : drums get more and more loud : it's the usual buildup towards the midboss, and guess what, it's a Haniwa ! The solution towards the sheer misery of the Human Spirits, the idols they pray for and who will vanquish the vile beasts for them, before the quietude again. Is it this quietude the return to normalcy under the beast spirits or the new Haniwa overlords ? It's not sure, but one things remain certain : it's still the Animal Realm, and it's not a good place to be ...
Stage 6 : No real impressions here, just your standard fare buildup to epicness. The song itself has parts of the final boss's theme, and as you get to the mid boss section, things relatively quiet down (but it's still part of the boss's theme). Theme of Eastern story plays as you blast your way through the silly human spirits who clearly forgot their place, meaningless distraction before the final confrontation.
Extra stage : same impression as stage 4 here overall, agressive percussion straight at the beginning in lieu of the agressive guitars, but still an agressive use of an instrument that captures the essence of Hell. It's the hell we've grown to be familiar with (we're back again), and the song overall feels less aggressive and forcceful than stage 4's aside from the more forcefull ZUNpets we get as we face the midboss, but it's more welcoming now. But we reach the end of the song and the harsh ZUNpets returns to remind you that this place is still Hell and of the threat that you're about to face ...
All in all, a relatively dramatic interpretation of the songs paired with understanding of the presented world this time. I've always considered Touhou 17's stage themes to be among the best when it comes to setting the atmosphere. Definitely quite a few ways away from SA's interpretation of Hell, where we have the adventurousness of spelunking in stage 1, the mystery and loneliness of stage 2, the festiveness of stage 3, the fanciness of Heartfelt Fancy, the loneliness and emptiness of stage 5, and the menace and bravery of stage 6. Touhou 17 tells a concise story based in the afterlife and in Hell, with undertones rooted in a dystopian form of modern society ... the instrumentation is also quite different from other titles, making Touhou 17's OST pretty interesting and unique, but probably heavy on the instruments-that-makes-it-sound-lonely on one side, and the very memorable harshness of Hell on the other
As for the characters themes, they're primarily about trying to encompass parts of the essence of characters. Therefore, my impression of them is so :
Eika's theme : the ingenious spirit who transformed Sai no Kawara's penance into a pleasant game, but no mistake here, she's got a bit of an attitude to show for those who try to cause trouble here. It's a song that tries to puff itself with a strong ZUNtar intro + ZUNriffs, but despite all that bravado, it's shows itself for what it truly is, in the cutsy repeatitive main part of the song : really just a little girl.
Urumi's theme : a weight manipulating cow-spider youkai. It sounds slow and dragged on, with suspicious instruments that try to emulate the Moo from the animals she's primarily based off. But despite the terror of the place you fight her with and her true nature, the slowness of the song reveals her for what she truly is : just a laid back youkai, quite eager to help us, possibly to break away from the monotony
Kutaka's theme : no real comment here, but it captures the liveliness of the chickens she stands for rather than any qualities / traits she has herself. A very hectic song, quite the discrepancy considering the sheer calmness of the previous stage 3 song. Chickens generally have a warm color, are associated with the sun, give the eggs you eat in the morning as well as greet the sunrise : they're very bright and cheerful creatures, and the sheer loudness and fast pace of the song captures them quite well
Kicchou's theme : one of the weirder themes. It's got like two distincts melodies, an aggressively beeping one that tries to aggrandize itself with these choirs and be threatening as when it gets faster, then, calm, slow whisttle-like instruments that keeps the insistant piano song after each time it plays ... then back to the beebing again but quieter, and then unto the whisttling. ZUN song climax typically have a lot of the previously used instruments make a return, but for her, the climax is ... quite quiet, not as loud as you'd expect of a ZUN climax, and retain the quiet, and urgent sounding tone it had previously ... all in all, a piece that doesn't grant the satisfaction of a grandiose climax but instead the pressure of one which give a sense of urgency. A relatively uncomfortable and oppressive piece, which lets you experience what feeling you'll have when confrontated by the boss of the Kiketsu Family, irresistible and insidious.
Mayumi's theme : comes off strong and slow, it's not scared or need to make a point. It's here, stalwart, and quite menacing as the guitars and beat combos come, and show it's rigidity in how its more rhythmic sections are consigned in very specific parts of the song. Highly rigid and almost mechanical, but beneath that, the bravery and resilience of the Haniwa corps : it's not afraid to get loud, to show you it's got teeth. A militaristic theme that's quite dignified in its quietude.
Keiki's theme : the craftsman god who reshaped the Beast Realm, one clay doll at a time. About as grandiose as you'd expect of, the piano just capture the glory and the greatness of such a respectable being, it's a song that's completely isolated from the struggle of the human spirits and the grudges of the animal spirits : it's pretty clear and loud, the ZUNpet gets pretty loud as it wants to sing eulogies towards her greatness, and the theme of Eastern story come around as a bonus to tell you that this is of importance. ZUN style climax is back here, it's a final boss theme-like final boss theme. Dunno what to really say here, but's it's quite a grand theme overall. No attempt to show quiet dignity like for Kanako, no reformed goddess-that-walks-among-us relaxed vibes like for Suwako, she's a major god who doesn't carry any baggage but just displays what she can do to its maximum.
Kurokoma's theme : a brave and bold sounding opening, it continues into a slow and cool, wild-west like fashion, then full stop : it gets slower. Quieter. Deeper. Darker. The piano slows down while the song gets more low key, and boom, it's back and really insistant on being low key ... and more menacing. Just like her theme, the leader of the Keiga family is a brave, bold and daring leader who is more than willing to handle the dirty deed herself, quite far from a saint. When the piano starts to slow down and you get more of those low keys, you figure it out : she's not one of the good guys. A theme that perfectly encapsulate her personality, it screams "villain" in the same vein as Seija's theme.
Overall, we still have ZUN's regular style where he set the mood with the music on one side, and tries to capture the characters on the other. Touhou 17's instrumentations is what make it stand aside from the previous games (every single one of which has their own unique vibes and instrumentation), and the insistence on fitting the mood for a Hell and afterlife game with dystopian undertones does trickle into the soundtrack imo. Games songs have a vague-ish intro before getting full blown, while music CDs can afford to have an ENTIRE track dedicated to being either the intro track of the final track with fitting mood. The lower points of the OST for me would be Urumi and Kicchou's themes, with potentially the stage 4 and extra ones with harsh instrumentations for me, but overall, I think ZUN succeeds at creating and capturing a particular kind of mood for this game.
Also no particularly big comment on the title screen, the ending screens theme, and the credits theme, just that the eerieness of the title screen (plus a relatively catchy start) makes it quite unique.
