Complex sentence: Baekhyun was a member of the school's band and attended several musical festivals, later winning an award at a local rock festival prior to joining S.M. Entertainment in 2011 through the S.M. Casting System.
Split into simpler sentences: Baekhyun was a member of the school's band and attended several musical festivals, later winning an award at a local rock festival. He joined S.M. Entertainment in 2011 through the S.M. Casting System.