Dana revealed that she used to be the vocal trainer of Girls' Generation's YoonA, Seohyun, former f(x) member Sulli, and Jessica.

SEE ALSO: Late singer Hara's mother loses inheritance lawsuit & constitutional court gives ruling

On KBS cool FM 'Park Myung Soo's Radio Show', DJ Park Myung Soo asked Dana, "Who were your students?" She answered, "I often taught Girls' Generation and f(x). YoonA, Seohyun, Jessica, Sulli, and others." 

She was also asked if she got mad at her students when they were unable to keep up. Dana responded, "I don't get mad at them. I don't let them notice that they are falling behind. For example, Jessica had the habit of not being able to project. So I fixed it by teaching her to sing pushing her back forward. Afterwards, Jessica was able to find her own color." 

Dana used to be a singer herself, but she currently is pursuing her career as a vocal trainer.