Among open-world adventure games in 2017, The Legend of Zelda: Breath of the Wild may have stolen some of Horizon Zero Dawn's thunder, but when it comes to soundtracks Horizon Zero Dawn OST comes out my top new original game soundtrack for the year. As you'd expect for a soundtrack of the genre, the music often leans more towards ambiance than outright melody, but there's no shortage of very pretty musical moments. Most frequently these are conveyed by beautiful solo and ensemble strings, often having a poignant sense of solitude as in "Homecoming" and "On Our Mother's Shoulders", though there are hopeful moments in folk-inspired tracks like "In Great Strides" and "City on the Mesa" as well. I believe there's not a single brass note throughout the score, and this case it feels entirely for the better.
Given the game's premise of mechanical beasts roaming a natural overworld, the soundtrack's mix of acoustic instrumentation with electronic synth could be expected as well. I have a hard time thinking of another soundtrack that pulls off the combination as seamlessly and with such consistently high quality as what composers Joris de Man and The Flight have done here though.
The soundtrack may not have the same number of memorable themes and highly dramatic musical moments of other top game OSTs, but as long as you're not expecting a quick melodic fix, you can listen through the entire run time without really feeling the need to touch the skip button, which is an exceedingly rare feet for a four-hour OST.