I really like Gensokyo Millennium ~ History of the Moon
More profound, more mature, and carrying a lot of things and burdens—this is my first impression of this song
The first segment carries a heavy sense of responsibility and history, like Eirin’s important status in the Lunar Capital and the glory she created. The second segment is filled with sorrow, melancholy, and a deep longing—just as Eirin wanted to come to the Earth to protect her beloved one, Princess Kaguya: she betrayed the Lunar Capital, slew the envoys of the Lunar Capital, and stayed with the Princess forever
I also picked up on some "sorrowful melodies"—they feel like Eirin’s homesickness. Eirin has actually been longing for the Lunar Capital all along, but her guilt towards Kaguya is far greater than that. The conflict between these two feelings really strikes a chord
I love the piano—it’s the second most representative instrument of Touhou, second only to the ZUNPet. Especially in TH8, the piano is widely used, and I’ve always thought the music of TH8 is the best in the series
Of course, Touhou music also needs to match the characters’ personalities and spell card designs—but I don’t want to go into too much detail here. You can easily find this information on Touhou Wiki
At the same time, I’m not a professional musician, so I can’t delve deeper into the connotations of this piece of music. These are just my personal emotional expressions