Selain Album, Mini Album dan Single, FTI juga mengisi soundtrack, antara lain:

인순이는예쁘다// In Suni neun Yeppeuda OST (In Soon Is Pretty OST)
Released: November 9, 2007
Track List:
사 랑을 보았나봐 // Sarangeul Boattnabwa (I Think I Saw Love)
못말리는결혼// Motmalli neun Gyeorhon OST (Unstoppable Marriage OST)
Released: November 9, 2007
Track List:
요즘 나는 // Yojeum naneun (Hong Ki & Nam Gyu-Ri from Seeya)
온에어// OnAeeo OST (On Air OST)
Released: March 20, 2008
Track List:

한가지 말 // Hangajimal (One Word)
연가// Yeon ga 2008 OST (special album with SG Wannabe & Choshinsung)
Released: April 3, 2008
Track List:
는물이 흐른다 // Neunmuli Heureunda (Tears Are Flowing)
OST. God of Study
Title: 모르시죠 // Moreusijyo
Singers: FT.triple // FT.triple
Album: 공부의 신 OST // God of Study OST
Release Date: 25 January 2010
OST. Heartstrings (2011)
Tracklist:
Kkogeun Anideorado (꼬근아니더라도)_It’s Not Necessary (Lagu ini juga terdapat di album Cross & Change)