Arranger
+ Composer composer;+\tMusician musician;+\tVocalist vocalist;
+ regVocalist(Vocalist vocalist):returnType+ regComposer(Composer composer)+ public void regMusician(Musician musician)+ requestDone()
Musician
+ boolean Idle=false+ Arranger arr
+ Musician(Arranger arranger)+ boolean isDone()+ String getDuty()+ void request()
Vocalist
Colleague
Composer
