이건 – 또
Track 01 from Single "또"
Release Date: 2017.10.23
이건 – 눈물 한잔
Track 01 from Single "눈물 한잔"
Release Date: 2021.06.17
서인영, 이건 – Someday
Track 01 from Single "숨바꼭질 OST Part.2"
Release Date: 2018.09.22
서인영, 이건 – Someday
Track 02 from Album "숨바꼭질 OST"
Release Date: 2018.12.15