Musical theory is somewhat of a misnomer,musical system or rules seems more direct.Knowing the musical theory or rules makes it possible to break them at strategic times and locations,which is the aim of most good composers,songwriters,players.Studying other types of music helps greatly in seeing and understanding examples of how,why,and when a writer chose to break a musical rule.However,the writer could never have broken the rule "correctly" if he didn't understand the rules(theory).Breaking musical rules (tastefully) and being able to return to the standard musical structure are vital to great writing.First,learn the rules,and then how to break them,because musical rules were meant to be broken.