The ultimate goal of this post is making a bunch of short explanations regard concepts from our world that had been used in Sound Horizon easily accesible. Many of these are already more or less well-known, but I truly believe that being concious of their existence inside of Sound Horizon can also improve one's comprehension of Revo's works and so I felt that giving everyone some pointers would be a good thing to do.

I'm mainly here to post my translations, but I will make this one exception for the sake of those pointers. It is already a part of SanhoraSpanish, in truth, but I thought that it could be also relevant for the english-speaking side of the fandom.

However, as I'm not an english translator, I can't point at all the different ways that the many english translations have adapted and will adapt these terms. And yet I think that this could be useful for those of you that aren't that knowledgeable about these matters.

• 樹氷(most commonly known as Tree Frost inside the fandom): This is the term that the japanese use to talk about a particular phenomenon from their islands. In winter, the trees in a certain area end up covered in frost and snow to the point they aren't recognisable as trees anymore. They were even known as "ice monsters", as youkai, by the locals.
  
  
• エレジー (the japanese version of the term elegy): It is a subgenre of poetry that focus mainly in lament and grief.
  
  
• 輪廻 (Samsara, or the endless cycle of death and rebirth): It is the word used for the concept of Samsara that is commonly found in eastern philosophies and religions. Its second name should speak well enough about its purpose. Besides that, breaking it is almost always thought to be the goal for those who believe in its existence.
  
  
• 輪舞曲/ロンド (Or rondo): It's a musical genre that mostly uses a main theme, which is used repeatedly over the song and it's alternated with different interludes or couplets.
  
  
• 因果 (Mostly known in western countries as karma): This concept comes from the dharmic religions, those that came from India, to talk about their idea of a kind of energy that was produced by people's actions. It keeps around even after the death of their creator, and so it ends up influencing their next life and how it will develop.
  
  
• 自我/エゴ (Ego or Self): This term is mainly only used for the idea of the "ego" in psychoanalysis, the one that Freud created together with the most commonly known Id (at least in SH).
  
  
• 澪音 (Or Rein): The kanji used for her name are worth getting an explanation. It could be translated as the "sound of a water course" and it also doubles as an homophone of the english Rain. Revo even makes uses of the verb for rainfall or snowfall in regards to Rein in ...Reloaded.
  
  
• 組曲 (Suite): This is the name used for a type of musical work composed of a set of pieces or movements. These are short, with each of them having different rhythm and tone.
  

THIS POST IS STILL A WORK-IN-PROGRESS

I've been given the blessing to mention some key things.

Quote :

自我/エゴ (Ego or Self): This term is mainly only used for the idea of the "ego" in psychoanalysis, the one that Freud created together with the most commonly known Id (at least in SH).

Through the perspective of Buddhism, this concept also appears within Sound Horizon itself, a good example being in IdoIdo. Elisabeth mentions her Impulse, as well as her Ego. This, through a Buddhist perspective would translate over to something bad. The idea goes to that desires and wants, and assertion of the self are what lead to unhappiness. Lafrenze' song directly states that if you get 1, you want 10, and so on. The idea of desire can never really be satiated through this perspective, so it is better to stop it all together.

"Ignorance", "Desire", and "Ego". While this is grounded in religious belief, it is still worth thinking about! With that said, do come to your own conclusions, and a big thanks to SanhoraSpanish ( @SanSP ) for this extra effort!

More may be added in the future.