Sylvalum's theme from Xenoblade Chronicles X, extended.
The track from the OST is titled 46:ri9 (Shiro no Tairiku), and contains both the day and night themes which play during the game.
My favorite nighttime field theme from this game.
Game: Xenoblade Chronicles X
Developers: Monolith Soft, Nintendo SPD
Publisher: Nintendo
Composer: Hiroyuki Sawano