Singer JOO has recently been swept into a slight controversy over her vocals. On the 15th, JOO made an appearance on MBC's Music Core where she sung her title song 'Bad Guy.' However, the singer showed a shaky voice while singing the song's high notes and was noticed for her shaky, unstable voice. JOO, who made her comeback after 2 years of further vocal training, left audience members feeling sympathetic towards the singer as she wasn't able to show off her usual powerful voice. Fans who viewed the stage performance also commented, "It seems like she really has a serious stage fright," "It seems like she was as nervous as she was greedy for singing well" and "It would be nice if she could get used to the stage quickly and show her powerful voice like before." Meanwhile, JOO is busy juggling her schedule between a singer and an actress for KBS drama 'Dream High.' Hopefully this was just a minor setback for the talented singer. Source: Newsen