It has now become a tradition for every new game to have a vocal theme, FFX-2 has not only one, but two vocal themes, both sung by Koda Kumi, the seiyuu for Lenne. Like in FFVIII, in FFX-2, the songs are actually existent in the game’s plot, where as in other games vocal themes are just thrown in for the heck of it and have no real significance to the storyline.
1000 Words on the other hand is definitely related to Lenne as she is the one who sings it during the FMV in the Thunder Plains. There she recounts her tale of her past through Yuna and the Singer Sphere and 1000 Words also has an orchestrated theme and a piano version!
Here are the lyrics for 1000 No Kotoba.
Here are the translated lyrics.
Both of FFX-2's English theme songs are sung by Jade from sweetbox.