The purpose of this study is to facilitate the comprehension of the differences between the job and the duties of both a Music Director and a Guest Conductor. These will be analyzed through the investigation of the work of Sir Andrew Davis, a famous conductor who has worked for many years dividing his time between the two different jobs. This study will focus on the importance of his achievements as the leader of one of the most important American opera theaters, and on the international appreciation of his work as a symphonic conductor. During the 2009-2010 season, I have observed Sir Andrew Davis during the productions he conducted at the Lyric Opera of Chicago. Starting in the same period, he has given periodic interviews with me for the following two years. I have focused on the different aspects of his job as Music Director finding several attributes that are unique to such a job. Besides, I have directly surveyed his job as a Guest Conductor and examined the approach that a conductor should give to guest conducting engagements. Finally, I have made a list of the requirements that emerging conductors should have while approaching a professional career in Maestro Davis's view.