Ji Yeon - Wishing On A Star
Kim Hyun Joong- Please
Sung Joon- Jaywalking
Big Bang - Love Dust
FT Island- Severely
Sean Lee, Rhymer, Huh In Chang - Victory (feat. Diana)

Finally found that ballad being played at Dream High 2 Ep 8's ending:

Lee Ki Chan, Sick of Hope


2NE1 - I Don't Care