For the music you depict, it can be as small as a specific scene in a book. It can be about a specific book or the entire series. It can be a theme of a specific part of the story: the characters, the places, the scenarios, etc.

How about styles and instruments?

In addition, what are some songs do you think fit the series, in some part or instance?

For me, when I first read the first part of Austraeoh, the first two songs that I thought fit the mood were the Theme of Limbo and Good ‘Ol Days from the Legend of Korra.

Also, how would you envision a soundtrack to the series?

(Sorry. I do not know much about music. I just want to provoke some thoughts for discussion.)

I’ll start with my depiction of a theme for Rainbow Dash, which was one of the things I was thinking about regarding music as I read the series. The funny thing is, I actually envision the theme to be different each book. She undergoes a lot of changes throughout the series from one book to the next.

For example:

In the beginning of the series in the first book Austraeoh, I imagined Rainbow Dash’s theme to somber and void, without any elements of her usual cocky but loyal character. She had just went through a very traumatic experience. She lost all of her friends and blames herself and Celestia for the events of the Mane Six, and she had lost all hope and care in the world and is striving to do the impossible before her inevitable death. In addition, she also prefers to be alone rather than being friends with the ponies she meet. I picture her character as null and void, so in terms of music, I imagine a scarce amount of music and music melody in the theme. Maybe just an ambient sound like the theme from Limbo.

In Eljunbyro, after her reawakening, she does not begin to lighten up to others quickly, such as Belle and Pilate, her first allies. In fact, she doesn’t start to lighten up to them until Belle provokes Rainbow Dash to open up to her in the story. As the story continues up to the end, you can see her character starting to rebuild piece by piece towards the allies she encounters such as Crimson and the Frazington soldiers in Foxtaur Forest. I imagine the theme would be not as void as in Austraeoh, but it still contains some of that emptiness. So besides the ambient sounds, there would be more notes and a melody played by instruments to accompany the sounds.

What do you guys think so far?

Also, since the entire Austraeoh series is based off of Norse mythology, I also thought the music would also have some Nordic elements in it.

So in thinking about this, the first thing that came to mind was actually the work of Yoko Kanno, who did soundtracks for Cowboy Bebop, Wolf's Rain, and Escaflowne, among others. Specifically I think Wolf's Rain fits well as the story there also involves a desperate journey to a distant paradise. I believe there are similar themes in Bebop as well except I haven't actually seen it

Kanno's instrumentation varies from classical "theatrical" orchestra to new age jazz and noise rock. Given the varied nature of setting and tone across the entire Austraeoh series, I think you would make a mistake to try and stick to a single genre or instrumentation set across multiple books. You could probably do it for single books at a time though, as I think it kind of falls naturally.

I feel I should keep this post short but I did want to highlight some more tracks that I think translate well to Austraeoh.

Yoko Kanno & The Seatbelts: Blue
Just an amazing song on its own right, about launching forward into a blue sky without regrets. Imagine this as the end of Urohringr.

Yoko Kanno & Maaya Sakamoto: Gravity
A mournful piano ballad contemplating giving up a difficult journey. This is the ending of Ynanhluutr.

Yoko Kanno & Steve Conte: Heaven's Not Enough
A rock ballad about deciding one's own future. Ending theme for Innavedr.

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I haven’t seen much of Yoko Kanno’s other works, but I am familiar with her work on Cowboy Bebop. I think Blue is a perfect fit for that part.

And yeah, I also agree that multiple genres should be used throughout the series as the themes and tones for each one differ greatly. Right now, I’m at the first part of Odrsjot (Around the time they went shopping in Grey Smoke), and I’m thinking some fast paced Celtic music could work. When I saw Rainbow Dash showing off, I thought of Le Repos Du Guerrier from Code Geass.

I don't have a specific theme for the series at large but anything from experimental electronica (Schnauss, Tobin, BoC) for the machine world and contemplative moments to orchestral scores for action scenes are what I've envisioned.

If I had to pick track that works for a single book then it'd be for Austraeoh itself. The apt lyrical translation really cements it:

I mostly just read it to the ost of Xenoblade Chronicles.

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(No links cause mobile, sorry!)
I will always be amazed by that Fate intro that argodaemon mapped to an sfm title sequence.

Aside from that, personally I see more of a Martin O'Donnel vibe here. He was the lead composer for Bungie projects like Halo 1, 2, etc and Destiny's original release. The vast diversity of styles he brings together with orchestral instruments, such as heavy brass and low drums for action sequences. Listen to The Rose from Music of the Spheres and tell me it doesn't bring to mind the military might seen in Eljunbyro and beyond. You can also use wide, sweeping strings and woodwinds for any sort of travelling.

Another thing that works is his collaboration on Halo 2 with Steve Vai, whose guitar tone to me would work really well for the machine world. That said for the enormity of the series I think it would also be very interesting to contemplate long tracts of footage where there's no scoring at all.

There are a couple of songs in spanish with lyrics that remind me of Austraeoh.
Un beso y una flor (A kiss and a flower), by Nino Bravo, speaks of someone leaving their home for a long journey. Lyrics mention Austraeoh themes like how even when one is alone, the idea or memory of a loved one would be like a light shining the way; light baggage for a long journey but a heart full of heavy sorrows; leaving behind what we love.

Caballo Salvaje (Wild Horse), by Rata Blanca, could speak of Rainbow Dash. The lyrics describe the subject of the song as a child of the lightning, shine of the sun. Mentions the way of the subject's way being marked by their heart, and about not looking back.

Of course in the chapters before every big final battle in the series, This is war by 30 Seconds to Mars plays in my head. It's an apic song and I also like to associate all the characters with the ones mentioned in each verse of the song.

Y’know, I’ve actually thought about asking this question for a while myself! Really interesting to hear everyone’s thoughts and music tastes.

Personally, Winners by Trampled by Turtles has always fit for me as the last few chapters of Odrsjot, as the Jury flies away into the distance. The lyrics and mood just match up so well.

Ooh, Belle by the Barr Brothers is a ridiculously good fit for Rainbow’s last conversation with Belle. Again, the lyrics match up really well — it’s like each of the lines of the verses is Rainbow talking to a different member of the Jury.

I wish I had more songs like these, but then again, I also wish Austraeoh were made into a TV show with its own soundtrack, so, y’know.

Since the last chapter of Innavedr was titled Toward the Sun, I've been associating it with this Estonian song whose title means the same. The mood and message of the song also fit the Austraeoh series quite well. Translation here.

I think thanks to this piece by argo, I seem to have picked Compass by Two Steps From Hell as the overall theme.

The lyrics seem to work well in regards to RD's determination and doubts, as well as having a light within (or pendant) to light your way ahead. I also imagine if the thing were to become an animated series that the intro to each book would have a montage of what that book is about with the instrumental version. Yeah, sounds like it would get as repetitive as the MLP:FiM theme, but at least visually each season's opening will be very different.
The beginning of the instrumental would fit all the somber or slow moments, like the scenery porn, remembering the past, opening up, or to the ending of many of the books where it ends on a good or sad note (Au El Ur Yn Ut). I can imagine the ending to Utaan getting this treatment: Axan's dying, RD's crying, final words and the gang forms a semicircle around the moment... aaand Credits!
(also the main part playing whenever RD lights up a machine world)

Speaking of the machine world, I feel like whenever RD explores it (or any other cave), or is about to encounter the symbol to open the doors, some Myst music would be nice here.

As for action parts, I only thought of generic action music (from starwars, lotr, or other epics). For miscellaneous slow parts I took some generic MLP background music.

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Somehow that sounds like it would fit a Chaos moment.

I recently read the ending to the Alafreo/Abinadi arc (The chapter where they were giving a toast.) while listening to this song, and I feel like it fits the tone of this part.

It gives several different emotions at once. It feels triumphant in how the brass and strings work together to harmonize, but it also feels melancholic and reflective, as if it beckons you to reflect on your life and what you’ve experienced. It coincides with the emotions that everyone on the Noble Jury felt after leaving Elma/Lerris behind. During the feast, they reflected upon all of the ponies they met, come and gone and then celebrated for Elma the changeling. Though they will miss her, she will be in their memories.
At the same time, it gives a sense of closure like a day that began and ends in achieving something that you desire. Just as Elma/Lerris found closure in meeting her original’s family and decided to stay with them, and just as another story arc has ended for the crew on a high note.