For me, my favourite all-time OST has to be Nobuo Uematsu's
Final Fantasy VIII. It's not just the music itself that is important to me; it's the fact that the score of this game taught me the basics of music, and how to compose music.
Final Fantasy VIII was the first of the series that I played, and I was in my early teens at the time. I hadn't had much musical education at that age, and I hadn't even been exposed to much music. Upon hearing the score for FFVIII, I suddenly released how important music was - not just in media, but also for personal joy. Uematsu's simple compositions laid the ground-work for my music theory knowledge, and also for my interest in composing my own music. By playing this game I learned how a piece of music should be composed for a love scene, a battle scene, a scene of sorrow, and many other situations. Using my ears I picked out the instrumentations, chord progressions, scales, and most important of all I discovered how important it was to captivate the ear with beautiful melodies. In this respect, Uematsu was my music teacher growing up.
I still listen to it every now and again. I think it holds up well for me via nostalgic value, as I actually think IX is a superior score, but VIII will always be my favourite OST due to the personal value is has to me. Without it I wouldn't be a composer!
Cheers, Nobuo Uematsu!
Player
