I say yes, the music contributes a lot to the game atmosphere. FF9 is medieval/fantasy and it's soundtrack is special, it has this medieval tone. For exemple Ipsen's castle track gives it an ancient/medieval atmosphere.
The music in FFIX has been a favorite of mine since it's debut. The game itself was such a wonderful addition in my eyes because it came in a with a fresh angle out of the years of VI-VIII. They really experimented in those games with a more technologically advanced feel. While I also loved it, it was really nice to change directions. At the same time, the nostalgic concept of earlier years was revisited and it ended up giving this game a very homey medieval feel. Straight back to it's roots. This required Nobuo to adjust the musical composition appropriately, and did he ever do a FANTASTIC job in my opinion. The warmth and character was reflected in it's tracks in the perfect way. The conceptual transition was a success across the board with this game, and the music was no exception. "You are Not Alone" for the overworld map is amongst my top favorite Final Fantasy songs of all time and I will never be able to keep myself from singing "Melodies of Life" if I hear it for the rest of my life.