Music historian: In the past, radio stations would not play rock songs that were more than three minutes in length  Rock musicians claimed that such commercial barriers limited their creativity, and some critics argue that only since those barriers have been lifted has rock music become artistic
In fact, however, when these barriers were lifted, the standards for song structures broke down and the music became aimless, because the styles from which rock derived were not well suited to songs of extended length
Rock music requires more discipline than some other forms of music.