György Orbán (b.1947) is a prominent Hungarian composer; his compositions include instrumental pieces, opera, film music, vocal and choral music. Among these works, his fondness of choral music is shown through the more than a hundred choral works he has composed. Orbán¡¦s choral works have combined traditional and modern elements and developed a unique style of his own. Choral lovers are deeply attracted to Orban¡¦s music and it has become very popular among international competitions and concerts these days. Orbán¡¦s Mass No.9 was commissioned by Ko Matsushita in the year 2000 for the ladies' choir ¡§Angelica¡¨ of the Kunitachi College of Music. Mass No.9 is a suite for a four-part female choir with piano accompaniment. This suite contains four pieces which are traditionally sung in Roman Catholic Mass. First is the Kyrie, a cry of repentance from the people to their Lord. Second is the Gloria, a praise sung to the Holy Trinity of the Father, Son and Holy Spirit. Third is the Sanctus-Benedictus, which consists of the Sanctus, praise to the glory of God, and the Benedictus, joyful shouting from the crowd as Jesus enters Jerusalem in full glory. Fourth is the Agnus Dei, a prayer to the Lamb of God for forgiveness. In the Kyrie, the texture of the music is built from thin to thick, and the pitch range moves from low to high, fully displaying the change in the people¡¦s emotion while they call upon the Lord three times. Meter change is used throughout the piece. At the end of this piece, in the piano accompaniment, a unique dance rhythm is created by accenting certain beats. In the Gloria¡Adotted notes and syncopated rhythm is used to create a forward-moving and lively atmosphere. In the first and third part of this piece, the choir sings together, praising God in the heaven; in the second part, only two soloists sing for the Lord¡¦s mercy. The textural difference creates contrasting sound within this piece. In Sanctus, the choir shows an obvious use of the pentatonic scale, and the music flows through a homophonic style while the piano part imitates the sound of a bell, all together creating solemnity and grandeur. In the latter part, a fugue theme runs through the Benedictus. With each part closely imitating the others, the fast tempo and short rhythm becomes a strong contrast to the Sanctus. In the Agnus Dei, the motif heard in the Kyrie is used once again, unifying the first and last piece of the Mass. This final piece is soothing and peaceful, the rhythm is simple and a few dissonant intervals are inserted to express the sin of the world. By combining beautiful melodies, different tonality and modes, changing meters and rhythms and by adding in many dissonant tones, Orbán created a unique style for Mass No.9, and thus this music have been highly received on the international stage. Besides the preface and conclusion, this master thesis consists of two parts. Part one includes a biographic sketch of György Orbán¡¦s life, his musical style and the different genres of his compositions. The second part consists of analysis and musical interpretation of the Mass No.9. There are two appendices at the end of this thesis. Appendix one contains e-mails between Ko Matsushita and the writer. Appendix two contains emails between Orbán and the writer.