Contrary to what many people think, the job of a DJ is more than just playing the songs that are in trend. It is a job of music selection thinking about the different musical genres and possible impact on the dance floor. Music is a transmitter of emotions and the DJ as a spokesperson is in charge of putting the right one.
Undoubtedly it is a process of constant practice and discipline. Creating almost imperceptible transitions between songs to change genres and to please a diverse audience is no easy task. Creating a music library and organizing it for quick access is no easy task. This among other things is called study, practice and dedication...and he does that off stage.